Blood-pressure targets in patients with recent lacunar stroke: the SPS3 randomised trial.

BACKGROUND: Lowering of blood pressure prevents stroke but optimum target levels to prevent recurrent stroke are unknown. We investigated the effects of different blood-pressure targets on the rate of recurrent stroke in patients with recent lacunar stroke. METHODS: In this randomised open-label trial, eligible patients lived in North America, Latin America, and Spain and had recent, MRI-defined symptomatic lacunar infarctions. Patients were recruited between March, 2003, and April, 2011, and randomly assigned, according to a two-by-two multifactorial design, to a systolic-blood-pressure target of 130-149 mm Hg or less than 130 mm Hg. The primary endpoint was reduction in all stroke (including ischaemic strokes and intracranial haemorrhages). Analysis was done by intention to treat. This study is registered with ClinicalTrials.gov, number NCT 00059306. FINDINGS: 3020 enrolled patients, 1519 in the higher-target group and 1501 in the lower-target group, were followed up for a mean of 3·7 (SD 2·0) years. Mean age was 63 (SD 11) years. After 1 year, mean systolic blood pressure was 138 mm Hg (95% CI 137-139) in the higher-target group and 127 mm Hg (95% CI 126-128) in the lower-target group. Non-significant rate reductions were seen for all stroke (hazard ratio 0·81, 95% CI 0·64-1·03, p=0·08), disabling or fatal stroke (0·81, 0·53-1·23, p=0·32), and the composite outcome of myocardial infarction or vascular death (0·84, 0·68-1·04, p=0·32) with the lower target. The rate of intracerebral haemorrhage was reduced significantly (0·37, 0·15-0·95, p=0·03). Treatment-related serious adverse events were infrequent. INTERPRETATION: Although the reduction in stroke was not significant, our results support that in patients with recent lacunar stroke, the use of a systolic-blood-pressure target of less than 130 mm Hg is likely to be beneficial. FUNDING: National Institutes of Health-National Institute of Neurological Disorders and Stroke (NIH-NINDS).

Albuminuria and the risk of incident stroke and stroke types in older adults.

BACKGROUND: The kidney biomarker that best reflects risk of stroke is unknown. We sought to evaluate the association of stroke with 3 kidney biomarkers: albuminuria, cystatin C, and glomerular filtration rate. METHODS: These 3 biomarkers were determined in 3,287 participants without history of stroke from the Cardiovascular Health Study, a longitudinal cohort study of men and women age 65 years and older from 4 US communities. The biomarkers were albuminuria ascertained using urinary albumin-to-creatinine ratio (UACR) from morning spot urine, creatinine-based estimated glomerular filtration rate (eGFR), and cystatin C. Outcomes were incident stroke (any, ischemic, or hemorrhagic) during follow-up between 1996 and 2006. RESULTS: A total of 390 participants had an incident stroke: 81% ischemic, 12% hemorrhagic, and 7% unclassified. In adjusted Cox regression models, UACR was more strongly related to any stroke, ischemic stroke, and hemorrhagic stroke than eGFR and cystatin C. The hazard ratio (HR) of any stroke comparing the top to bottom quintile of UACR was 2.10 (95% confidence interval [CI] 1.47-3.00), while HR for eGFR was 1.29 (95% CI 0.91-1.84) and for cystatin C was 1.22 (95% CI 0.85-1.74). When considering clinically relevant categories, elevated UACR was associated with increased hazard of any stroke and ischemic stroke regardless of eGFR or cystatin C categories. CONCLUSIONS: UACR was the kidney biomarker most strongly associated with risk of incident stroke. Results in this elderly cohort may not be applicable to younger populations. These findings suggest that measures of glomerular filtration and permeability have differential effects on stroke risk.

Bioactive nitric oxide concentration does not increase during reactive hyperemia in human skin.

This study examined whether nitric oxide (NO) is involved in the cutaneous response to reactive hyperemia (RH) in the human forearm. We enrolled seven healthy volunteers. NO concentrations were monitored using a NO selective amperometric electrode (ISO-NOP200, World Precision Instruments) inserted into the skin of the forearm. Laser-Doppler flowmetry (Moor Instruments) was used for monitoring skin blood flow (SkBF) at the same site. SkBF and NO levels were monitored and recorded continuously throughout the experiment. An intradermal microdialysis probe was inserted adjacent to the NO electrode for drug delivery. Data collection began 140 min after the NO electrodes and microdialysis probes were inserted. RH was achieved by the inflation of a blood pressure cuff to 25 mmHg above systolic pressure for 7 min after which the pressure in the cuff was abruptly released. Acetylcholine (ACh) was given by microdialysis probe at the end of RH study to verify the ability of the electrode system to detect changes in the NO concentration. SkBF and NO data before RH and immediately, 2, 5, 7, and 10 min after cuff deflation were used for analysis. SkBF increased immediately after release of the occlusion (P < 0.0001) and remained elevated for 2 min. No significant NO changes occurred with the increases in LDF. ACh induced increases in both SkBF and NO (P < 0.000 and P < 0.037, respectively). We conclude that RH increases SkBF by mechanisms that do not require a measurable increase in NO concentrations.

Bradykinin does not mediate cutaneous active vasodilation during heat stress in humans.

To test the hypothesis that bradykinin effects cutaneous active vasodilation during hyperthermia, we examined whether the increase in skin blood flow (SkBF) during heat stress was affected by blockade of bradykinin B(2) receptors with the receptor antagonist HOE-140. Two adjacent sites on the forearm were instrumented with intradermal microdialysis probes for local delivery of drugs in eight healthy subjects. HOE-140 was dissolved in Ringer solution (40 microM) and perfused at one site, whereas the second site was perfused with Ringer alone. SkBF was monitored by laser-Doppler flowmetry (LDF) at both sites. Mean arterial pressure (MAP) was monitored from a finger, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF/MAP). Water-perfused suits were used to control body temperature and evoke hyperthermia. After hyperthermia, both microdialysis sites were perfused with 28 mM nitroprusside to effect maximal vasodilation. During hyperthermia, CVC increased at HOE-140 (69 +/- 2% maximal CVC, P < 0.01) and untreated sites (65 +/- 2% maximal CVC, P < 0.01). These responses did not differ between sites (P > 0.05). Because the bradykinin B(2)-receptor antagonist HOE-140 did not alter SkBF responses to heat stress, we conclude that bradykinin does not mediate cutaneous active vasodilation.

Selected contribution: Gender differences in the endothelin-B receptor contribution to basal cutaneous vascular tone in humans.

To test whether the contribution of endothelin-B (ET-B) receptors to resting vascular tone differs between genders, we administered the ET-B receptor antagonist BQ-788 into the forearm skin of 11 male and 11 female subjects by intradermal microdialysis. Skin blood flow was measured using laser-Doppler flowmetry at the microdialysis site. The probe was perfused with Ringer solution alone, followed by BQ-788 (150 nM) and finally sodium nitroprusside (28 mM) to effect maximal cutaneous vasodilation. Cutaneous vascular conductance (CVC) was calculated (laser-Doppler flowmetry/mean arterial pressure) and normalized to maximal levels (%max). In male subjects, baseline CVC was (mean +/- SE) 19 +/- 3%max and increased to 26 +/- 5%max with BQ-788 (P < 0.05 vs. baseline). In female subjects, baseline CVC was 13 +/- 1%max and decreased to 10 +/- 1%max in response to BQ-788. CVC responses to BQ-788 differed with gender (P < 0.05); thus the contribution of ET-B receptors to resting cutaneous vascular tone differs between men and women. In men, ET-B receptors mediate tonic vasoconstriction, whereas, in women, ET-B receptors mediate tonic vasodilation.

Kidney transplantation during the first trimester of pregnancy: immunosuppression with mycophenolate mofetil, tacrolimus, and prednisone.

We present a case of living, related-donor kidney transplantation during the first trimester of pregnancy. The patient received mycophenolate mofetil (MMF), tacrolimus, and prednisone throughout the entire pregnancy. This is the first reported case of use of MMF during pregnancy. The mother did well, except for mild preeclampsia and mild renal insufficiency at term. The baby girl was born prematurely at week 353/7. The only possible teratogenic effects detected included hypoplastic nails and short fifth fingers. No chromosomal abnormalities were found. The child is growing and developing normally. Although we do not recommend the use of mycophenolate mofetil during pregnancy based on this experience, it is reassuring to know that a successful outcome can be expected in mothers treated with MMF during pregnancy.

Spironolactone-induced agranulocytosis.

OBJECTIVE: To report a case of agranulocytosis secondary to spironolactone in a patient with cryptogenic liver disease. CASE SUMMARY: A 58-year-old Hispanic woman with cryptogenic cirrhosis was admitted to University Hospital on October 31, 1995. Laboratory data revealed a leukocyte count of 1.0 x 10(3)/mm3 and an absolute neutrophil count (ANC) of 10 cells/mm3. Prior to treatment with spironolactone, the leukocyte count was 10.2 x 10(3)/mm3 and ANC 8400 cells/mm3. Agranulocytosis resolved 5 days following the discontinuation of spironolactone. Results from the bone marrow biopsies before and after treatment with spironolactone suggested that agranulocytosis was caused by the drug's toxic effect on the bone marrow. DISCUSSION: Drug-induced agranulocytosis is a serious adverse effect, occurring at a rate of approximately 6.2 cases per million persons each year. In addition to the case reported here, three other reports of agranulocytosis secondary to spironolactone have been published in the literature. Several factors have been identified that may increase a patient's risk for developing agranulocytosis, including increased age, hepatic or renal impairment, drug dosage and duration, and concurrent medications. CONCLUSIONS: Agranulocytosis secondary to spironolactone is a serious potential adverse effect. Patients with risk factors for developing this adverse effect should be closely monitored since early detection and discontinuation of spironolactone can improve prognosis.

Control of skin blood flow by whole body and local skin cooling in exercising humans.

We examined the independent roles of whole body skin temperature (Tsk) and tissue temperature (local temperature, Tloc) in the control of skin blood flow (SBF) during cooling and the roles of the vasoconstrictor (VC) and active vasodilator (AVD) systems in mediating these effects. SBF was monitored by laser-Doppler flowmetry (LDF) at untreated sites and sites with local VC blockade by pretreatment with bretylium (BT). Seven subjects underwent four sessions of moderate bicycle exercise (20-30 min duration) at neutral Tsk and Tloc (34 degrees C), neutral Tsk and cool Tloc (27 degrees C), low Tsk (28 degrees C) and neutral Tloc, and low Tsk and Tloc. Cutaneous vascular conductance (CVC; LDF/mean arterial pressure) was expressed relative to the maximum. Cool Tsk increased the threshold level of internal temperature at which CVC began to rise equally at BT-treated and untreated sites (P < 0.05). The rate of increase in CVC relative to internal temperature was reduced by local cooling. BT pretreatment partially reversed this effect (P < 0.05). Thus a cool environment results in reflex inhibition of the onset of AVD activity by cool Tsk and a reduced rate of increase in CVC due, in part, to norepinephrine release stimulated by cool Tloc.

Cutaneous active vasodilation in humans is mediated by cholinergic nerve cotransmission.

During heat stress, increases in blood flow in nonglabrous skin in humans are mediated through active vasodilation by an unknown neurotransmitter mechanism. To investigate this mechanism, a three-part study was performed to determine the following: (1) Is muscarinic receptor activation necessary for active cutaneous vasodilation? We iontophoretically applied atropine to a small area of forearm skin. At that site and an untreated control site, we measured the vasomotor (laser-Doppler blood flow [LDF]) and sudomotor (relative humidity) responses to whole-body heat stress. Blood pressure was monitored. Cutaneous vascular conductance (CVC) was calculated (LDF divided by mean arterial pressure). Sweating was blocked at treated sites only. CVC rose at both sites (P < .05 at each site); thus, cutaneous active vasodilation is not effected through muscarinic receptors. (2) Are nonmuscarinic cholinergic receptors present on cutaneous arterioles? Acetylcholine (ACh) was iontophoretically applied to forearm skin at sites pretreated by atropine iontophoresis and at untreated sites. ACh increased CVC at untreated sites (P < .05) but not at atropinized sites. Thus, the only functional cholinergic receptors on cutaneous vessels are muscarinic. (3) Does cutaneous active vasodilation involve cholinergic nerve cotransmission? Botulinum toxin was injected intradermally in the forearm to block release of ACh and any coreleased neurotransmitters. Heat stress was performed as in part 1 of the study. At treated sites, CVC and relative humidity remained at baseline levels during heat stress (P > .05). Active vasodilator and sudomotor responses to heat stress were abolished by botulinum toxin. We conclude that cholinergic nerve activation mediates cutaneous active vasodilation through release of an unknown cotransmitter, not through ACh.

The effect of iontophoresis on the cutaneous vasculature: evidence for current-induced hyperemia.

Combining laser-Doppler blood flux measurements of the skin microcirculation with iontophoresis of vasoactive agents is a promising noninvasive tool for pharmacological studies. However, preliminary observations in our laboratories suggested significant current-associated vasodilation when an expected vasoconstrictor (NG-monomethyl-L-arginine acetate) was iontophoresed. The present study was designed to define nonspecific current-related versus specific pharmacological effects of iontophoretically administered ions on the cutaneous vasculature. Dose-response studies to a series of anions (nitrite, chloride, acetate, and bicarbonate) and cations (sodium, lithium, and acetylcholine) were carried out in six healthy volunteers (three male) by iontophoresis to the forearm skin on separate days. Laser-Doppler flux was measured at the same sites. All ions caused dose-dependent vasodilation. There was no difference in the response between chloride, bicarbonate, or acetate and nitrite, the nitric oxide donor. The acetylcholine dose response was shifted rightward after atropine pretreatment. Cutaneous vascular responses to iontophoresis comprise nonspecific, current-induced hyperemia and specific effects of the administered agent. Acetylcholine appears to cause muscarinic and current-induced dilatation. Nitrite may cause current-induced hyperemia alone. Current-induced hyperemia should be considered in interpreting the acute cutaneous vascular responses to iontophoretically administered agents in humans.

Skin of the dorsal aspect of human hands and fingers possesses an active vasodilator system.

To test for an active vasodilator system in human hand and finger skin, seven subjects had a small area of dorsal hand, palm, or dorsal finger pretreated with bretylium (BT) to block adrenergic vasoconstriction. Skin blood flow was monitored at a BT-treated site, a comparable untreated site, and the forearm by laser-Doppler flowmetry. Cutaneous vascular conductance (CVC) was evaluated from the ratio of blood flow to arterial pressure. Body cooling, to evaluate vasoconstrictor system blockade, caused CVC at untreated sites of forearm, palm, dorsal hand, and dorsal finger to fall by 45 +/- 4, 85 +/- 5, 51 +/- 9, and 63 +/- 7%, respectively (all P < 0.05). At BT-treated sites of palm, dorsal hand, and dorsal finger, reductions in CVC were only 13 +/- 3, 2 +/- 18, and 13 +/- 4%, respectively (dorsal hand not significant, others P < 0.05). With body heating, increases in CVC at untreated sites of forearm, palm, dorsal hand, and dorsal finger were 881 +/- 165, 779 +/- 368, 423 +/- 115, and 1,430 +/- 716%, respectively (all P < 0.05). At BT-treated sites of palm, dorsal hand, and dorsal finger, increases were 35 +/- 15, 342 +/- 107, and 343 +/- 34%, respectively (palm not significant, others P < 0.05). Increased CVC at the palm began after 1.2 +/- 0.2 min of heating, significantly earlier than forearm (11.8 +/- 2.5 min), dorsal hand (16.4 +/- 3.4 min), or dorsal finger (15.6 +/- 3.6 min), which did not differ significantly from one another.(ABSTRACT TRUNCATED AT 250 WORDS)

Reflex control of active cutaneous vasodilation by skin temperature in humans.

The purpose of this study was to examine whether reflex effects of changes in whole body skin temperature (Tsk) on cutaneous vasculature are mediated through the vasoconstrictor or the active vasodilator arm of the sympathetic nervous system. In six subjects, reflex responses in forearm skin blood flow (SkBF) to changes in Tsk were monitored by laser-Doppler flowmetry. SkBF was monitored at a control site and at a 0.6-cm2 site where bretylium (BT) had been iontophoretically applied to abolish sympathetic vasoconstrictor control. Reflex control of SkBF at BT-treated sites is solely through active vasodilator activity. An index of cutaneous vascular conductance (CVC) was calculated from the blood flow signal and mean arterial pressure, measured noninvasively. Data are expressed relative to maximum CVC (CVCmax) achieved by local warming of measurement sites to 42 degrees C at the end of each study. Tsk was controlled with a water-perfused suit covering the entire body except for the head and arms. Esophageal temperature (Tes) was measured as an index of internal temperature. In part A (rest), raising Tsk at rest from 31.9 +/- 0.3 to 36.7 +/- 0.2 degrees C increased CVC at control sites from 3 +/- 0.2 to 5 +/- 0.6% of CVCmax. CVC did not change at BT-treated sites, suggesting that at rest, with a normal internal temperature, reflex effects of raising Tsk on SkBF are mediated through vasoconstrictor withdrawal. In part B (exercise), exercise at a low Tsk increased Tes to 37.49 +/- 0.1 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of sympathetic nerves in the vascular effects of local temperature in human forearm skin.

The role of adrenergic nerve function in the cutaneous vascular response to changes in local skin temperature in the human forearm was examined using three protocols: 1) blocking release of norepinephrine presynaptically by local iontophoresis of bretylium (BT), 2) altering background adrenergic tone by changing whole body skin temperature, and 3) blocking cutaneous nerves by proximal infiltration of local anesthetic. Forearm skin blood flow was measured by laser-Doppler flowmetry (LDF) and cutaneous vascular conductance (CVC) was calculated as LDF/blood pressure. In protocol 1, local cooling (29 degrees C) elicited a rapid and sustained fall in CVC at control sites (-43 +/- 8%) in contrast to a biphasic response at BT-treated sites, consisting of an initial vasodilation followed by a vasoconstriction (percent change CVC = 28 +/- 13 and -34 +/- 18, respectively). Local warming (39 degrees C) increased CVC at control and at BT-treated sites by 331 +/- 46 and 139 +/- 31%, respectively. In protocol 2, at a neutral, cool, or warm whole body skin temperature, local cooling (29 degrees C) elicited similar reductions in CVC (-34 +/- 8, -29 +/- 5, and -30 +/- 4%, respectively), and local warming (38 degrees C) produced similar increases in CVC (89 +/- 15, 85 +/- 21, and 74 +/- 22%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of control of skin blood flow during prolonged exercise in humans.

Exercise in a warm environment raises internal temperature and leads to a rapid increase in skin blood flow (SkBF). As exercise continues, and internal temperature approaches 38 degrees C, the rate of rise of SkBF is markedly attenuated despite further significant increases in internal temperature. To find whether this attenuation is mediated by increased cutaneous active vasoconstrictor activity or by a reduced rate of rise of active vasodilator activity, each of 12 male subjects had 0.64 cm2 forearm skin sites iontophoretically treated with bretylium tosylate for selective local blockade of noradrenergic vasoconstrictor nerves. SkBF was monitored there and at adjacent untreated control sites by laser-Doppler blood flowmetry (LDF). Whole body skin temperature (Tsk) was controlled by water-perfused suits, and esophageal temperature (Tes) was monitored as an index of internal temperature. Mean arterial pressure (MAP) was monitored and cutaneous vascular conductance was calculated as LDF/MAP. Sweat rate was also monitored by dew point hygrometry in 11 subjects. Tsk was raised to 38 degrees C, after which subjects began 20-30 min of exercise on a bicycle ergometer. The rate of the initial rapid increase in SkBF with increasing Tes was not altered by bretylium treatment (P > 0.05 between sites). The attenuation of the rate of rise during the latter phase of exercise was not abolished by bretylium treatment (P > 0.05 between sites); instead, there was a trend for the attenuation to be enhanced at those sites. We conclude that the attenuated rate of rise of SkBF is due to limitation of active vasodilator activity and not due to increased vasoconstrictor tone.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of serotonin on vasopressin release: a comparison to corticosterone, prolactin and renin.

Previously we reported that 5 min after intracerebroventricular (i.c.v.) injection, serotonin (5-HT, 2.5 micrograms) produced increases in blood pressure and decreases in heart rate in conscious rats that were blocked by LY 53857 (a selective 5-HT2/1C antagonist) and were sensitive to vasopressin antagonism. The present studies were performed to determine if this dose of 5-HT acts similarly to increase plasma vasopressin levels. In addition, the vasopressin responses were compared to prolactin, corticosterone, and plasma renin activity, three other neuroendocrine systems regulated in part by 5-HT. The administration of 5-HT (2.5 micrograms i.c.v.) produced a rapid (maximum response in less than 5 min) and brief (return to baseline by 15 min) increase in plasma vasopressin levels. The response was eliminated by the centrally acting 5-HT2/1C antagonist LY 53857 (100 micrograms/kg i.v.), but only attenuated by xylamidine (100 micrograms/kg i.v.), a 5-HT2/1C antagonist that reportedly does not cross the blood-brain barrier. 5-HT also increased plasma prolactin and corticosterone levels, but neither LY 53857 nor xylamidine altered these responses. In rats rendered chronically baroreceptor deficient by sinoaortic deafferentation, the vasopressin response to 5-HT was reduced, whereas the prolactin response was normal. 5-HT did not increase plasma renin activity in intact or baroreceptor-deficient rats, in contrast to the other neuroendocrine systems studied. Thus, the data demonstrate that vasopressin levels are elevated briefly following 5-HT i.c.v., consistent with the pharmacologic profile of the early cardiovascular response.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of central serotonin on autonomic control of heart rate in intact and baroreceptor deficient rats.

The intracerebroventricular (i.c.v.) injection of serotonin (5-HT) increases blood pressure and decreases heart rate (HR) in conscious rats by activation of 5-HT2/1C receptors. Since the bradycardia is eliminated by pretreatment with a ganglionic or V1-vasopressin antagonist, we proposed that the decrease in HR results from an effect on cardiac autonomic activity which is potentiated by vasopressin. The present study aimed first, to further characterize mechanisms by which the i.c.v. injection of 5-HT (2.5 micrograms) decreases HR in conscious rats, and second to determine the cardiovascular responses to 5-HT (2.5 micrograms, i.c.v.) in rats with chronic sinoaortic deafferentation (SAD). In intact rats, the bradycardia elicited by 5-HT was eliminated by a combination of the muscarinic antagonist atropine and the beta-adrenoceptor antagonist sotalol; neither antagonist was effective alone. In rats with SAD, 5-HT produced a larger increase in blood pressure and a marked tachycardia, both of which were eliminated by the 5-HT2/1C antagonist LY 53857. Furthermore, in rats with SAD the 5-HT-induced increase in HR was blocked by sotalol alone. In conclusion, 5-HT (2.5 micrograms, i.c.v.) acts on central 5-HT2/1C receptors to increase arterial pressure. In intact rats this decreases HR by vasopressin-potentiated activation of baroreceptor reflexes and subsequent increase in vagal tone and decrease in cardiac sympathetic tone. In the absence of baroreflexes, a direct central effect of 5-HT to produce a beta-adrenoceptor-mediated cardioacceleration is unmasked.

Pharmacological evidence that circumventricular organs may participate in the pressor effect of central serotonin.

The present study was to investigate the role of '5-HT2-like' receptors in the circumventricular organs in the pressor response elicited by the central injection of serotonin (5-HT) to conscious rats. The increase in blood pressure induced by intracerebroventricular (i.c.v.) 5-HT (2.5 micrograms) was attenuated by intravenous pretreatment will, the peripheral 5-HT2 antagonist xylamidine (100 or 300 micrograms/kg). A combination of xylamidine with prazosin or a V1-vasopressin antagonist did not produce a further attenuation in the pressor response. Our data suggest that when administered i.c.v., 5-HT increases blood pressure by acting on 5-HT2-like receptors located in circumventricular organs as well as areas of the brain protected by the blood-brain barrier.

Vasopressin and autonomic mechanisms mediate cardiovascular actions of central serotonin.

Intracerebroventricular administration of serotonin (5-HT) to conscious rats increases mean arterial pressure (MAP) and decreases heart rate. To determine the mechanisms involved, 5-HT (2.5 micrograms) was injected intracerebroventricularly into conscious rats pretreated with various neurotransmitter and hormone antagonists. The selective 5-HT2 antagonist LY 53857 abolished the increase in MAP and the bradycardia elicited by 5-HT. The increase in MAP produced by 5-HT was potentiated by chlorisondamine (a ganglionic antagonist), unaffected by prazosin (an alpha 1-antagonist) or a vasopressin V1 antagonist alone, but eliminated by the combined pretreatment with prazosin plus the vasopressin antagonist. In contrast, the bradycardia was eliminated by either the vasopressin V1 antagonist or chlorisondamine. In conclusion, 5-HT injected into the lateral cerebral ventricle of conscious rats induces sympathoexcitation and the release of vasopressin, which results in an increase in MAP; 5-HT also elicits a bradycardia mediated through an interaction of the autonomic nervous system with circulating vasopressin.

Quipazine increases renin release by a peripheral hemodynamic mechanism.

Systemically administered serotonin (5-HT) agonists have been suggested to act centrally to increase plasma renin activity (PRA) and arterial pressure (AP). To test this hypothesis, hemodynamic responses were determined in conscious male rats after intracerebroventricular (i.c.v.) or intravenous (i.v.) administration of the direct 5-HT agonist quipazine. When administered i.v., quipazine increased AP and PRA, and decreased renal blood flow (RBF); doses of quipazine i.c.v. that increased AP to a similar degree failed to increase PRA. The increase in PRA elicited by i.v. quipazine was not blocked by propranolol, suggesting non-neural mechanisms. The increase in AP and decrease in RBF elicited by i.v. quipazine were not eliminated by prazosin, enalapril, or a V1-vasopressin antagonist administered alone or in combination. LY 53857, a 5-HT2 antagonist that enters the central nervous system (CNS), blocked all responses to i.v. quipazine. In contrast, the peripheral 5-HT2 antagonist xylamidine blocked the renin and RBF responses, but only attenuated the pressor response to quipazine. These data suggest that quipazine can act in the CNS to increase AP, but when administered systemically quipazine also activates vascular 5-HT2 receptors to increase AP further and to decrease RBF. The increase in PRA caused by i.v. quipazine is secondary to renal hemodynamics and is unrelated to CNS actions of this drug.