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The present study was undertaken to assess the effect of prazosin, a selective postsynaptic alpha 1-adrenergic receptor blocking agent, on normoxic and hypoxic mice, in order to evaluate experimentally its use in the treatment of the excessive erythrocytosis that characterizes chronic mountain sickness. The drug, injected intraperitoneally to adult mice at a dose of 400 micrograms/kg per day, induced a significant depression of the rate or erythropoiesis, as measured by red blood cell 59iron uptake, with a decrease in the hematocrit from the 3rd day. The drug also inhibited the oxygen-dependent secretion of erythropoietin (estimated by the plasma immunoreactive hormone concentration) in hypoxemic mice when injected between 0 and 2 h after initiation of the hypoxic stimulation. When injected daily into mice exposed to intermittent hypobaric hypoxia, prazosin limited the degree of polycythemia or induced a sustained decrease in the hematocrit when polycythemia was already present due to previous exposure. It is postulated that the drug, by reducing the peripheral vascular resistance seen during hypoxia, could increase renal blood flow, thus improving the renal oxygen supply and partially restoring the imbalance between gas supply and demand, which drives erythropoietin formation.
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beta-Amyloid peptides (Abetas) share with lipopolysaccharide, a potent pro-inflammatory agent, the property of stimulating glial cells or macrophages to induce various inflammatory mediators. We recently reported that central administration of lipopolysaccharide induces peripheral interleukin-6 responses via both the central and peripheral norepinephrine system. In this study, the effect of intracerebroventricular injection of various synthetic Abetas on plasma interleukin-6 levels was examined in mice. Abeta(1-42) dose-dependently increased plasma interleukin-6 levels: 'aged' Abeta(1-42) was more effective than fresh, whereas Abeta(42-1) had no effect. 'Aged' Abeta(1-42) (205 pmol/mouse i.c.v.)-induced plasma interleukin-6 peaked at 2 h post injection, which is earlier than the peak time of the Abeta(1-42)-induced brain interleukin-6, tumor necrosis factor-alpha and interleukin-1beta levels, which was 4, 4 and 24 h, respectively. Among various peripheral organs, Abeta(1-42) (205 pmol/mouse i.c.v.) significantly increased interleukin-6 mRNA expression in lymph nodes and liver. Abeta(1-42) (205 pmol/mouse i.c.v.) significantly increased norepinephrine turnover in both hypothalamus and spleen. Either central or peripheral norepinephrine depletion effectively inhibited the Abeta(1-42)-induced peripheral interleukin-6 response. Pretreatment with prazosin (alpha(1)-adrenergic antagonist), yohimbine (alpha(2)-adrenergic antagonist), and ICI-118,551 (beta(2)-adrenergic antagonist), but not with betaxolol (beta(1)-adrenergic antagonist), inhibited Abeta(1-42)-induced plasma interleukin-6 levels. These results demonstrate that centrally administered Abeta(1-42) effectively induces the systemic interleukin-6 response which is mediated, in part, by central Abeta(1-42)-induced activation of the central and the peripheral norepinephrine systems.
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We have recently assigned a major stimulatory role to the brain catecholamines (CA) via alpha 1 and beta receptors on CRH-ACTH secretion, e.g. in the physiological response to stress. In the present study, we explored the possible participation in this regulation of post-synaptic alpha 2 receptors in free moving rats, one week after CA denervation of the hypothalamus by bilateral neurotoxic lesions of the noradrenergic ascending brain stem bundles (NAB). Intracerebroventricular (i.c.v.) injection of clonidine (alpha 2 agonist; 1 nmol) induced a 3 fold rise of ACTH release (measured by RIA) above vehicle (PBS) injected controls (p less than 0.001). This stimulatory effect was completely reversed by an i.c.v. pretreatment with the alpha 2 antagonist idazoxan (10 nmol; without action by itself), whereas it was only slightly affected by an i.c.v. pretreatment with a combination of an alpha 1 and beta blocker (prazosin + propranolol; 5/5 nmol; p greater than 0.1). The results strongly suggest the participation of alpha 2 post-synaptic receptors in the central catecholaminergic activation of ACTH secretion.
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Caffeine and other methylxanthines induce a dose-dependent reduction in core body temperature in mice. These experiments investigated the effects of neurotransmitter and neuromodulator antagonists on caffeine-induced hypothermia. Pretreatment with the alpha 2-adrenoceptor antagonist, atipamezole; the beta-adrenoceptor antagonist, propranolol; the dopamine antagonist, haloperidol; or the benzodiazepine receptor antagonist, flumazenil had no intrinsic effects on core body temperature nor did they interact significantly with the hypothermic effects of caffeine. The alpha 1-adrenoceptor antagonist, prazosin and the 5-HT receptor antagonist, metergoline significantly enhanced the hypothermic effects of caffeine, probably involving a combined effect with their intrinsic hypothermic actions. Pretreatment with the opiate receptor antagonist, naloxone (3 mg/kg i.p.), had no intrinsic effect on core body temperature but attenuated the hypothermic effect of caffeine reflected in a parallel shift to the right in the caffeine dose-effect curve. The naloxone-induced attenuation of the hypothermic effects of caffeine was also seen to be dose-dependent. The results reveal that opiate receptors (but not adrenoceptors, 5-HT, dopamine or benzodiazepine receptors) may play a role in modulating the hypothermic action of caffeine and possibly other methylxanthines.
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Melatonin receptors were characterized in the brains of three mammals (rabbit, horse and sheep) by an in vitro binding technique, using 2-[125I]iodomelatonin as labelled ligand. Although binding sites for melatonin have been described recently in several vertebrate species (including the sheep), the rabbit and the horse have not been the subject of investigation so far. Apart from characterization, the present report describes receptor distribution in a number of brain regions, thus allowing for direct interspecies comparison under the same methodological conditions. 2-[125I]iodomelatonin labelled high-affinity binding sites in crude membrane preparations from these species. A series of kinetic and saturation experiments revealed that the binding was rapid, stable, saturable, reversible, of high affinity (Kd in the low picomolar range) and low capacity (Bmax between 1 and 20 fmol/mg protein). The competition studies showed that the relative order of potency of a variety of indoles for inhibition of 2-[125I]iodomelatonin binding was as follows: 2-iodomelatonin greater than 6-chloromelatonin greater than melatonin much much greater than 5-methoxytryptophol greater than 5-methoxytryptamine, and that it was similar in the different brain regions. Prazosin, which has been reported as an extremely potent melatonin analog in the hamster brain, possessed no potency in all preparations from different regions in the three species under investigation. The regional distribution of the receptor showed insignificant species differences. Highest density was always recorded in the median eminence/pars tuberalis (ME/PT) area. Other regions (SCN, POA and certain cortical areas), showed lower, but significant, receptor content. Saturation and competition studies revealed that these binding sites were also of high affinity, low capacity and high specificity.(ABSTRACT TRUNCATED AT 250 WORDS)
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A single infusion of oxaliplatin, which is widely used to treat metastatic colorectal cancer, induces specific sensory neurotoxicity signs that are triggered or aggravated when exposed to cold or mechanical stimuli. Bee Venom (BV) has been traditionally used in Korea to treat various pain symptoms. Our recent study demonstrated that BV alleviates oxaliplatin-induced cold allodynia in rats, via noradrenergic and serotonergic analgesic pathways. In this study, we have further investigated whether BV derived phospholipase A2 (bvPLA2) attenuates oxaliplatin-induced cold and mechanical allodynia in mice and its mechanism. The behavioral signs of cold and mechanical allodynia were evaluated by acetone and a von Frey hair test on the hind paw, respectively. The significant allodynia signs were observed from one day after an oxaliplatin injection (6 mg/kg, i.p.). Daily administration of bvPLA2 (0.2 mg/kg, i.p.) for five consecutive days markedly attenuated cold and mechanical allodynia, which was more potent than the effect of BV (1 mg/kg, i.p.). The depletion of noradrenaline by an injection of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride (DSP4, 50 mg/kg, i.p.) blocked the analgesic effect of bvPLA2, whereas the depletion of serotonin by injecting DL-p-chlorophenylalanine (PCPA, 150 mg/kg, i.p.) for three successive days did not. Furthermore, idazoxan (α2-adrenegic receptor antagonist, 1 mg/kg, i.p.) completely blocked bvPLA2-induced anti-allodynic action, whereas prazosin (α1-adrenegic antagonist, 10 mg/kg, i.p.) did not. These results suggest that bvPLA2 treatment strongly alleviates oxaliplatin-induced acute cold and mechanical allodynia in mice through the activation of the noradrenergic system, via α2-adrenegic receptors, but not via the serotonergic system.
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It is estimated that 25% to 30% of patients with heart failure (HE) in the United States are black. Compared with nonblack patients, black patients have a reduced ability to produce endogenous nitric oxide, which may be associated with enhanced responsiveness to drugs that increase the delivery of nitric oxide, such as nitrates. When used with nitrates, hydralazine (HYD) acts as an antioxidant and prevents development of nitrate tolerance.
Concern based on the reported short-term adverse effects of antihypertensive agents on plasma lipid and lipoprotein profiles (PLPPs) has complicated the therapy for hypertension.
The effects of drugs with selective action on alpha 1- or alpha 2-adrenoceptors were investigated on persistent head twitches, vertical neck dyskinesia, and the random circling behaviors induced by chronic intraperitoneal injections of IDPN. The alpha agonist clonidine and the alpha antagonist prazosin inhibited the IDPN-induced behavioral syndrome whereas the alpha antagonist yohimbine had no significant effect. These results suggest that dysregulation of a facilitatory noradrenergic input to cortical and/or subcortical motor areas may be involved in the abnormal movements caused by chronic treatment with IDPN.
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Investigation of the effects of the different adrenoceptor (AR) subtypes in memory formation may reveal discrete actions of noradrenaline in memory modulation and storage mediated through particular AR subtypes. Noradrenaline injected intracerebrally in the chick produced biphasic effects on memory consolidation with enhancement at low doses and inhibition at high doses. We have previously shown that the enhancement by the lower doses of noradrenaline is attributable to actions at beta2- and beta3-adrenoceptors, whereas the inhibitory effect of higher doses is attributable to alpha1-adrenoceptors. The present studies show that the inhibition of memory by high doses of noradrenaline is mimicked by the alpha1-AR agonist methoxamine, and the dose-response curve is shifted to the right by pretreatment with the alpha1-AR antagonist prazosin. alpha1-ARs may play a critical role in memory formation in highly stressful situations, when noradrenaline levels are high in particular brain regions. It is not known where the alpha1-ARs responsible for the effect on memory are localized. alpha1-ARs are found on neurons and astrocytes and in the cerebral vasculature and therefore the action of high doses of noradrenaline via alpha1-AR agonists could be via an action at any of these sites. Activation of alpha1-adrenoceptors in the intermediate hyperstriatum ventrale in the chick forebrain by the alpha1 adrenoceptor agonist methoxamine inhibits the consolidation of memory. Because the same effect is produced by high levels of noradrenaline, it is likely that stimulation of alpha1-ARs is the mechanism underlying this effect.
A total of 45 patients who participated in a multicenter trial was evaluated with urodynamic pressure-flow studies before and after 26 weeks of treatment.
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1 Possible involvement of sympathetic purinergic transmission in the neurogenic response of dog cerebral and basilar arteries was examined with the use of alpha, beta-methylene ATP and adrenoceptor, cholinoceptor blocking agents. 2 In the isolated basilar arteries, electrical transmural stimulation produced a transient contraction which was frequently followed by a relaxation. This transient contraction was abolished after desensitization of P2-purinoceptors with alpha, beta-methylene ATP or by treatment with guanethidine. The relaxant response induced by electrical stimulation was also attenuated but was not abolished by such treatments. Prazosin, propranolol and atropine had no significant effect on the responses to electrical stimulation. Yohimbine augmented both the contractile and relaxant responses. 3 In most preparations of the dog middle cerebral arteries, electrical transmural stimulation produced only a relaxation. This relaxation was little affected after treatment with alpha, beta-methylene ATP or guanethidine, and was not inhibited by the other adrenoceptor and cholinoceptor blocking agents. 4 Tetrodotoxin abolished the responses induced by electrical transmural stimulation in both the basilar and middle cerebral arteries. 5 Exogenous ATP (10(-6) and 10(-5)M) produced a transient contraction followed by a relaxation of the basilar arteries and a relaxation of the middle cerebral arteries. Desensitization of P2-purinoceptors abolished the contractile response to ATP without affecting the amplitude of relaxation. 6. In the basilar and middle cerebral arteries preincubated with [3H]-noradrenaline, electrical transmural stimulation evoked an increase in 3H-efflux and this response was markedly inhibited by guanethidine or tetrodotoxin but was not affected by alpha, beta-methylene ATP. Yohimbine increased the evoked 3H-efflux. 7. These findings indicate that cerebral arteries of the dog are innervated by sympathetic purinergic nerves and non-sympathetic nerves which liberate unknown vasodilator substance(s), and that the former nerves are more dominant in the neurogenic response to electrical stimulation of the dog basilar artery than in the middle cerebral artery.
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Endothelin-1 (ET-1) (10 pmol) microinjected into the superficial layer of superior colliculus induces decreases in blood pressure (control, 108 +/- 5 mmHg, n=6; ET-1, 71 +/- 4 mmHg, n=5). The effects on blood pressure induced by endothelin-1 were significantly (p<0.05) reduced by pre-administration into the superior colliculus of the alpha1-adrenoceptor agonist phenylephrine (1 nmol) (46 +/- 5%, n=5), beta1-adrenoceptor antagonist acebutolol (5 nmol) (51 +/- 6%, n=5) or beta1/beta2-adrenoceptor antagonist propranolol (3.4 nmol) (51 +/- 11%, n=5). In contrast, endothelin-1-induced effects were increased (p<0.05) by microinjections into the superior colliculus of prazosin (2.4 nmol) (49 +/- 7%, n=5), an alpha1-adrenoceptor antagonist; dobutamine (4 nmol) (51 +/- 9%, n=5), a beta1-adrenoceptor agonist or isoprenaline (1 nmol) (49 +/- 6%, n=5), a beta1/beta2-adrenoceptor agonist. No involvement of alpha2- or beta2-adrenoceptors has been detected. Therefore, ET-1 induces decreases in blood pressure with selective involvement of alpha1- and beta1-adrenoceptors.
In vivo prostatic secretion was collected from retired breeder Sprague Dawley rats using a method for isolated perfusion of the rat prostatic urethra. Enzymatic acid phosphatase determination was performed on the collected effluent. Control acid phosphatase secretion was 24.2 +/- 2.7 nm over 30 minutes. Intravenous phenylephrine 5 mg/kg stimulated a 10 fold increase in acid phosphatase secretion. The secretion seen with phenylephrine was dose dependent and could be blocked with prazosin, but not yohimbine, atropine, or propranolol. Intravenous beta-adrenergic agonist isoproterenol caused no increase in the secretion of rat prostatic acid phosphatase. Intravenous administration of the cholinergic agonist pilocarpine also resulted in a dose dependent rise in acid phosphatase secretion. The stimulation seen could be blocked by atropine but not phentolamine or propranolol. The stimulation of acid phosphatase secretion seen with alpha 1 adrenergic or cholinergic agonists was not additive. Intravenous vasoactive intestinal peptide did not stimulate acid phosphatase secretion nor did it augment the secretion induced by alpha 1 adrenergic or cholinergic agonists. Release of acid phosphatase into rat prostatic exocrine secretion is under both alpha 1 adrenergic and cholinergic control.
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Clo reversed the changes of the myocardial beta-AR-AC-cAMP system resulted from the scalds in rats.
We studied the effects of hydralazine, nicardipine, nitroglycerin, and fenoldopam (a dopamine D1-agonist) on isolated human umbilical arteries (HUA) from patients classified as normotensive and with pregnancy-induced hypertension (PIH). Umbilical artery rings were contracted with the thromboxane A(2) analog (U46619; 10(-8) M) and then exposed to cumulative concentrations of fenoldopam, hydralazine, nicardipine, and nitroglycerin. Second, rings were preexposed to prazosin (10(-5) M), phenoxybenzamine (10(-5) M), or none, and the constriction responses to increasing doses of fenoldopam or dopamine were recorded. Nitroglycerin, hydralazine, and nicardipine produced concentration-dependent relaxation of U46619-preconstricted HUA segments from normotensive and PIH patients. Fenoldopam and dopamine induced umbilical artery constriction in both normal and PIH rings at concentrations > or = 10(-5) M and > or = 10(-3) M, respectively. Phenoxybenzamine, but not prazosin, pretreatment irreversibly abolished fenoldopam-induced contraction. In this in vitro study, nitroglycerin was the most potent vasodilator of the HUA constricted with U46619, followed by nicardipine and hydralazine. However, fenoldopam constricted HUA rings only at supratherapeutic concentrations. No significant differences of vascular responses to fenoldopam (P = 0.3534), nitroglycerin (P = 0.7416), nicardipine (P = 0.0615), and hydralazine (P = 0.5514) between rings from normotensive or hypertensive pregnant patients were shown.
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1. Neurotransmitters released from nerve endings are inactivated by re-uptake into the presynaptic nerve terminals and possibly into neighbouring glial cells. While analysing the functional properties of alpha 1-adrenoceptors in the hypothalamus, we observed a high-affinity uptake process for noradrenaline in postsynaptic peptidergic neurones. 2. In primary hypothalamic cell cultures and in a hypothalamic neuronal cell line, [3H]-prazosin bound with high affinity and was displaced by unlabelled prazosin in concentrations of 10(-10) to 10(-7) M. However, at concentrations of unlabelled prazosin above 10(-7) M, there was a paradoxical increase in apparent [3H]-prazosin binding. 3. Methoxamine, an alpha 1-adrenoceptor ligand that is not subject to significant neuronal uptake, displaced [3H]-prazosin but did not cause the paradoxical increase in the apparent binding of [3H]-prazosin. Cooling the cells to 4 degrees C reduced the total amount of prazosin associated with the cells; under these conditions, methoxamine almost completely inhibited [3H]-prazosin binding to the cells. 4. In the presence of desipramine (DMI), unlabelled prazosin displaced [3H]-prazosin as before, but no paradoxical increase in apparent binding was seen above 10(-7) M. 5. The paradoxical increase of [3H]-prazosin binding was not observed in membrane preparations of hypothalamic neurones. These findings indicated that the paradoxical increase in apparent [3H]-prazosin binding was due to a cellular uptake process that becomes evident at high concentrations of the ligand. 6. DMI (10(-5) M) had no effect on the specific binding of [3H]-prazosin. The presence of alpha1-adrenoceptors was confirmed by binding of -HEAT, but [3H]-idazoxan (an alpha2- ligand) did not bind to the cells.7. The uptake of prazosin obeyed the Michaelis-Menten model, with similar Km and Vmax values in both types of cultures.8. Noradrenaline was taken up with high affinity by both types of cultures. (+/-)-[3H]-noradrenaline uptake was reduced by DMI and by excluding sodium from the medium, indicating that this process has some of the properties of uptake 1. (+/-)-[3H]-noradrenaline uptake in the cell line was unaffected by testosterone.9. The measured uptake of (-)-noradrenaline in the cell line was considerably increased by blockade of catechol-omicron-methyl-transferase and monoamine oxidase, suggesting that (-)-noradrenaline is metabolized to lipophilic products that escape across the plasma membrane.10. Studies in rats, in which the noradrenaline isomer 6-hydroxydopamine was used, suggested that the post synaptic uptake process is operative in hypothalamic CRH and vasopressin neurones in vivo.11. The Km for (-)-noradrenaline was within the range for the high affinity uptake, process in noradrenergic neurones. Uptake takes place in concentrations at which noradrenaline activates alpha1-adrenoceptors.Removal of noradrenaline from the vicinity of the receptors may prevent desensitization,thus maintaining the responsiveness of postsynaptic neurones to the actions of the neurotransmitter.
We investigated the role of alpha-adrenergic antagonists and clonidine injected into the medial septal area (MSA) on water intake and the decrease in Na+, K+ and urine elicited by ANGII injection into the third ventricle (3rdV). Male Holtzman rats with stainless steel cannulas implanted into the 3rdV and MSA were used. ANGII (12 nmol/ micro l) increased water intake (12.5 +/- 1.7 ml/120 min). Clonidine (20 nmol/ micro l) injected into the MSA reduced the ANGII-induced water intake (2.9 +/- 0.5 ml/120 min). Pretreatment with 80 nmol/ micro l yohimbine or prazosin into the MSA also reduced the ANGII-induced water intake (3.0 +/- 0.4 and 3.1 +/- 0.2 ml/120 min, respectively). Yohimbine + prazosin + clonidine injected into the MSA abolished the ANGII-induced water intake (0.2 +/- 0.1 and 0.2 +/- 0.1 ml/120 min, respectively). ANGII reduced Na+ (23 +/- 7 micro Eq/120 min), K+ (27 +/- 3 micro Eq/120 min) and urine volume (4.3 +/- 0.9 ml/120 min). Clonidine increased the parameters above. Clonidine injected into the MSA abolished the inhibitory effect of ANGII on urinary sodium. Yohimbine injected into the MSA also abolished the inhibitory effects of ANGII. Yohimbine + clonidine attenuated the inhibitory effects of ANGII. Prazosin injected into the MSA did not cause changes in ANGII responses. Prazosin + clonidine attenuated the inhibitory effects of ANGII. The results showed that MSA injections of alpha1- and alpha2-antagonists decreased ANGII-induced water intake, and abolished the Na+, K+ and urine decrease induced by ANGII into the 3rdV. These findings suggest the involvement of septal alpha1- and alpha2-adrenergic receptors in water intake and electrolyte and urine excretion induced by central ANGII.
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The aim was to analyse the influence of coronary postjunctional alpha 1 and alpha 2 adrenergic vasoconstriction in hypoperfused myocardium with special emphasis on transmural distribution of blood flow.
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The present study shows, for the first time, that urinary bladder distention caused vasoconstriction of coronary conduit and resistance vessels involved mechanisms related to alpha1 adrenoceptors. Pretreated administration of doxazosin reversed the changes toward baseline. Vasoconstriction during bladder distention can be relieved after nitroglycerin administration, suggesting an unchanged responsiveness of vascular smooth muscle cells to such distention.
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ABCG2, a transporter of the ATP-binding cassette family, is known to play a prominent role in the absorption, distribution, metabolism, and excretion of xenobiotics. Drug-transporter interactions are commonly screened by high-throughput systems using transfected insect and/or human cell lines. The determination of ABCG2-ATPase activity is one method to identify ABCG2 substrate and inhibitors. We demonstrate that the ATPase activities of the human ABCG2 transfected Sf9 cell membranes (MXR-Sf9) and ABCG2-overexpressing human cell membranes (MXR-M) differ. Variation due to disparity in the glycosylation level of the protein had no effect on the transporter. The influence of cholesterol on ABCG2-ATPase activity was investigated because the lipid compositions of insect and human cells are largely different from each other. Differences in cholesterol content, shown by cholesterol loading and depletion experiments, conferred the difference in stimulation of basal ABCG2-ATPase of the two cell membranes. Basal ABCG2-ATPase activity could be stimulated by sulfasalazine, prazosin, and topotecan, known substrates of ABCG2 in cholesterol-loaded MXR-Sf9 and MXR-M cell membranes. In contrast, ABCG2-ATPase could not be stimulated in MXR-Sf9 or in cholesterol-depleted MXR-M membranes. Moreover, cholesterol loading significantly improved the drug transport into inside-out membrane vesicles prepared from MXR-Sf9 cells. MXR-M and cholesterol-loaded MXR-Sf9 cell membranes displayed similar ABCG2-ATPase activity and vesicular transport. Our study indicates an essential role of membrane cholesterol for the function of ABCG2.
Posttraumatic stress disorder (PTSD) is a psychiatric disorder with symptoms that include insomnia due to hyperarousal and recurring nightmares. These symptoms are believed to be due to a conditioned response that is regulated by norepinephrine. Prazosin, an α(1) antagonist, can decrease levels of norepinephrine in the central nervous system, thereby reducing nightmares related to PTSD.
Human BPH tissue possesses both alpha 1H- and alpha 1L-adrenoceptor subtypes according to the affinities for prazosin, and only the alpha 1H subtype can be completely inhibited by some concentration of phenoxybenzamine. Treatment by alpha 1 blocker may not change the conditions of alpha 1-adrenoceptors in prostatic tissue.
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The use of cardiovascular medications can have a variety of neuropsychiatric consequences. Many cardiovascular agents cause higher rates of fatigue and sedation than placebo, and case reports of medication-induced mood syndromes, psychosis, and cognitive disturbances exist for many cardiovascular drugs. Depression has been associated with P3-blockers, methyldopa, and reserpine, but more recent syntheses of the data have suggested that these associations are much weaker than originally believed. Though low cholesterol levels have been associated with depression and suicide, lipid-lowering agents have not been associated with these adverse effects. Finally, cardiovascular medications may have beneficial neuropsychiatric consequences; for example, the use of clonidine in patients with attention deficit-hyperactivity disorder, the use of prazosin for patients with post-traumatic stress disorder; and the use of propranolol for performance anxiety and akathisia.
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The effects of the nonpeptide angiotensin II receptor antagonist losartan and the angiotensin-converting enzyme inhibitor captopril on pressor responses to the selective alpha 1-adrenoceptor agonist cirazoline (10 ng/kg-3.0 mg/kg) in the pithed rat were compared. In addition, the effects of losartan and captopril on pressor responses to cirazoline were compared in the presence of the selective irreversible alpha 1-adrenoceptor antagonist SZL-49 (1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-(2-bicyclo[2,2,2]octa-2,5- dienyl-carbonyl)-piperzine) and/or the Ca2+ channel antagonist nifedipine. Losartan (5.0 mg/kg) and captopril (3.0 mg/kg), as compared to saline, significantly lowered the blood pressure of intact, anaesthetized and pithed rats. Continuous infusion with vasopressin was used to restore the blood pressure of pithed rats pretreated with losartan or captopril to a level comparable to animals that had received saline. Losartan, captopril, nifedipine (1.0 mg/kg), and SZL-49 (10.0 mg/kg) antagonized the pressor actions of cirazoline, which displaced the dose-diastolic blood pressure response curve for the agonist to the right. Moreover, pressor responses to cirazoline were significantly reduced in rats that had received losartan and nifedipine in comparison to nifedipine alone. In contrast, in rats treated with nifedipine, further administration of captopril did not significantly reduce pressor responses to cirazoline as compared to nifedipine alone. Cirazoline-mediated pressor responses at all doses were significantly attenuated in rats treated with SZL-49 and either losartan or nifedipine combined as compared to SZL-49 alone. In contrast, only cirazoline-mediated pressor responses at lower doses were significantly reduced by pretreatment with a combination of SZL-49 and captopril as compared to SZL-49 alone.(ABSTRACT TRUNCATED AT 250 WORDS)
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A transient peak of cytosolic calmodulin (CaM) was produced during the prereplicative phase of rat liver cell proliferation following partial hepatectomy. After accumulating in the cytosol, CaM apparently translocated into the nuclei, associating with the nuclear matrix. The administration of alpha 1-adrenergic blockers to hepatectomized rats prevented the association of CaM with the nuclear matrix without affecting the increase in the total nuclear CaM. The inhibitory effect of the alpha 1-antagonists was reversed by the simultaneous injection of the alpha-agonist noradrenaline. Since the activation of alpha 1-adrenergic receptors results in the release of Ca2+ from endoplasmic reticulum stores, the results suggest that the association of CaM with the nuclear matrix during proliferative activation is mediated by Ca2+ released from endoplasmic reticulum and show that the association with the matrix is independent of its intranuclear accumulation.
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A series of substituted phenethyl derivatives of 3-benzisothiazolylpiperazine incorporating potent D2 and 5-HT2A antagonist activity was investigated as an approach to a novel atypical antipsychotic agent. The in vitro profile of 8e from this series is a combination of D2 receptor affinity comparable to the typical antipsychotic agent haloperidol and a 5-HT2A/D2 ratio comparable to the atypical agent clozapine. In vivo 8e possesses activity consistent with an efficacious antipsychotic agent with less tendency to induce extrapyramidal side effects in man.
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The role of alpha 2-adrenergic receptor stimulation in the regulation of systemic vascular capacity and venous return, a major determinant of cardiac output, is not well understood. With the influence of the central nervous system isolated from the systemic circulation, the direct peripheral vascular effects of two specific, chemically distinct alpha 2-adrenergic receptor agonists, UK 14,304 and B-HT 920, were investigated in 19 dogs on total cardiopulmonary bypass with constant arterial perfusion and central venous pressure. Five-minute intra-arterial infusions of UK 14,304 (200 micrograms/min) resulted in increased arterial resistance (mean arterial pressure increased 18 +/- 4 [SEM] mm Hg; p less than 0.01) and a decrease in systemic vascular capacity (81 +/- 20 ml; p less than 0.01). This decrease in systemic vascular capacity appears to result from vasoconstriction, since there was no decrease in transhepatic resistance to portal flow and no significant change in hepatic vein flow to suggest redistribution of arterial blood flow. Yohimbine abolished both the arterial and systemic capacity effects, whereas prazosin did not. Intra-arterial administration of B-HT 920 (200 theta grams/min) in five dogs produced similar changes in arterial resistance and systemic capacity. These findings provide direct evidence for beta 2-adrenergic control, not only of arterial resistance but also of systemic vascular capacity, which in the intact animal would increase venous return to the heart.
The VA Academic Detailing Service Informatics Toolset provides prescribing, demographic and risk factor data for veterans with PTSD treated at the White River Junction VA Medical Center (WRJ VA) and affiliated rural clinics in Vermont and New Hampshire. Individualized academic detailing visits were provided to clinicians identified by the informatics tool with the aim of increasing guideline-concordant care. Other educational efforts included traditional, didactic group education on evidence-based PTSD care and the development and dissemination of educational materials for clinicians and patients. Prescribing trends of benzodiazepines, off-label atypical antipsychotics, and prazosin were collected quarterly for 2 years (January 1, 2014 to March 30, 2016).
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Two young adult monkeys (Macaca mullata) were trained to perform a delayed-response task that required the monkeys to remember a cued spatial position (left or right) over a delay interval and then to make a response to the cued position. Local injection of the alpha 2-adrenergic antagonist yohimbine (10 micrograms in 2 microliters saline) into the dorsolateral prefrontal cortex (Walker's area 46 and area 9) impaired the performance of the delayed-response task, and it was without effect on the performance of the task if there was no delay between the cue and choice signals. The main performing error after injection of yohimbine was that the monkeys responded to uncued position with higher rate. Local injection of the alpha 1-adrenergic antagonist prazosin (10 microgram in 2 microliters saline) or the beta-adrenergic antagonist propranolol (10 micrograms in 2 microliters saline) into the same cortical areas induced no significant effect on the performance of the task. The present study suggests that prefrontal alpha 2-adrenoceptors play an important role in the spatial working memory in young adult monkeys.
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Inhibition of alpha(2)-adrenoceptors caused transient dilation that was substantially greater than the contribution of alpha(2)-adrenoceptors to the constriction. This reflects a slowly reversing alpha(2)-adrenoceptor-mediated endothelium-dependent dilation and provides a rapid, sensitive test of alpha(2)-adrenoceptor activity. This approach also clearly emphasizes the poor selectivity of phenylephrine at vascular alpha-adrenoceptors.
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1. alpha 1-Adrenoceptor activation caused two separate effects in rat dorsal raphe neurons: a depolarization and an increase in the duration of the after-hyperpolarization following the action potential. The depolarization often resulted in repetitive action potentials. The alpha 1-adrenoceptor antagonists prazosin and WB 4101 blocked the depolarization induced by phenylephrine. The concentration-response curve to phenylephrine was shifted to the right by WB 4101. 2. Under voltage clamp, alpha 1-adrenoceptor agonists caused an inward current at -60 mV, which often became smaller at negative potentials but rarely reversed polarity even at strongly negative potentials. Using whole-cell recording, the inward current reversed polarity at the equilibrium potential for potassium in the majority of cells. Intracellular Cs+ decreased or abolished the alpha 1-mediated inward current. The inward current was dependent on external calcium, but not on the degree of internal calcium buffering. Removal of external calcium or addition of MgCl2, CoCl2 or CdCl2 reduced or blocked the effects of alpha 1-adrenoceptor agonists. Barium and strontium supported and even augmented the inward current induced by alpha 1-adrenoceptor agonists, whereas nifedipine and omega-conous toxin had no effect. In contrast, internal dialysis with the calcium chelator 1,2-bis(O-aminophenoxy)ethane-N,N,N'N'-tetraacetic acid (BAPTA) did not inhibit the inward current. 3. The alpha 1-induced depolarization was blocked (or occluded) by the inclusion of GTP-gamma-S (100 microM) in the recording pipette. The phorbol-ester 4-phorbol 12,13-dibutyrate (PDBu) had no action on the membrane potential and depressed the phenylephrine-induced depolarization. This depression was reversed by the non-selective protein kinase inhibitor staurosporin. 4. Phenylephrine and noradrenaline increased a late component of the after-hyperpolarization (late-AHP) that followed a single action potential. The alpha 1-sensitive late-AHP was blocked by apamine suggesting that it is a calcium-dependent potassium conductance. 5. Thapsigargin reduced the duration of the late-AHP and blocked the phenylephrine-mediated prolongation. Caffeine also augmented the late-AHP and ryanodine blocked the augmentation induced by caffeine. The augmentation induced by phenylephrine was not occluded by caffeine and was still present after the caffeine-induced augmentation was blocked by ryanodine. 6. In slices pretreated with manoalide the depolarization induced by alpha 1-agonists was not changed; however, the late-AHP was reduced in duration and the alpha 1-receptor-mediated augmentation of the late-AHP was decreased.(ABSTRACT TRUNCATED AT 400 WORDS)
Quantitative in vitro autoradiographic methods were used to examine for the effect of repeated administration of electroconvulsive shock (ECS) on binding to subtypes of the alpha-1 receptor in rat brain. Rats were treated once daily for 10 d with ECS or sham ECS, then killed, and brains were removed and sectioned for autoradiographic analysis. Total alpha-1 binding (including both alpha-1a and alpha-1b subtypes) was assessed with [3H]prazosin; alpha-1b binding was assessed with [3H]prazosin in the presence of 10 nM WB4 101 to mask alpha-1a binding; and alpha-1a binding was assessed with [3H]WB4 101. ECS caused a significant increase in [3H]prazosin binding in most cortical regions: this increase was confined to a band corresponding to cortical laminae I-III. Subtype analysis indicated that the increase in cortical binding was due to an increase in binding to the alpha-1b subtype. Dense alpha-1 binding was detected in most thalamic nuclei: however, only 1 small area, the parafascicular nucleus, showed a significant increase in alpha-1 binding following repeated ECS. The only other region where ECS was shown to significantly affect alpha-1 binding was the amygdala. Binding to all regions of the amygdala except the central nuclei was increased by ECS: in the lateral amygdala, this was due primarily to an increase in alpha-1b binding, while in the remaining regions the increase was primarily an alpha-1a phenomenon. Thus the effect of repeated ECS on alpha-1 binding in rat brain was found to be confined to several specific regions of the cortex, thalamus, and amygdala. Furthermore, in each of these regions, the ECS effect was limited to 1 or the other of the 2 subtypes of the alpha-1 receptor.
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Plasma adiponectin levels were correlated with the total cholesterol (r = -0.244, P = 0.017), triglyceride (r = -0.306, P = 0.002), high-density lipoprotein-cholesterol (r = 0.286, P = 0.005), body mass index (r = -374, P < 0.001), systolic (r = -502, P < 0.001) and diastolic blood pressures (r = -235, P = 0.021). The independent predictors of plasma adiponectin levels were HOMA (beta = -0.199, P = 0.02), body mass index (beta = -0.313, P < 0.001) and systolic blood pressures (beta = -0.483, P < 0.001). Ramipril and valsartan increased the plasma adiponectin levels significantly higher than the other regimens (P < 0.05 for both) while metoprolol did not make a significant effect.
How can we treat patients with reduced morphine doses without loosing the pain killing effect or morphine antinociceptive effects (MAE)? To address this question, we hypothesized that serotonin (5-HT2) receptor antagonism could enhance MAE mediated by kappa-opioid receptors. We pretreated mice with ketanserin, a 5-HT2 receptor antagonist, and measured the morphine dose required to observe analgesia. The morphine dose effective in 50% of animals (ED(50)) was reduced from 4.7 to 1.3mg/kg, and the morphine dose effective in 100% of animals (ED(max)) from 13.7 to 2.5mg/kg. Ketanserin has a similar enhancer effect when morphine, which has a dual role via mu and kappa receptors, was substituted by the antinociceptive spiradoline, a selective κ-opioid agonist. At a morphine dose of 3.5mg/kg, 30% of the mice showed antinociceptive behaviour, rising to 100% when ketanserin was co-administered and then reduced to 20% in the presence of nor-binaltorphimine, a kappa-opioid receptor antagonist. Our data strongly suggests a serotonergic inhibition of the kappa-opioid component of MAE and the possibility that this serotonergic inhibition could be reversed through 5-HT2 receptor antagonism.
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Randomized, double-blind, multicenter (eight government and private facilities), placebo-controlled study.