Cardiac baroreflex facilitation evoked by hypothalamus and prefrontal cortex stimulation: role of the nucleus tractus solitarius 5-HT2A receptors.
نویسندگان
چکیده
We previously showed that serotonin (5-HT2) receptor activation in the nucleus of the tractus solitarius (NTS) produced hypotension, bradycardia, and facilitation of the baroreflex bradycardia. Activation of the preoptic area (POA) of the hypothalamus, which is involved in shock-evoked passive behaviors, induces similar modifications. In addition, previous studies showed that blockade of the infralimbic (IL) part of the medial prefrontal cortex, which sends projections to POA, produced an inhibitory influence on the baroreflex cardiac response. Thus, to assess the possible implication of NTS 5-HT2 receptors in passive cardiovascular responses, we analyzed in anesthetized rats the effects of NTS inhibition and NTS 5-HT2 receptor blockade on the cardiovascular modifications induced by chemical (0.3 M D,L-homocysteic acid) and electrical (50 Hz, 150-200 microA) stimulation of IL or POA. Intra-NTS microinjections of muscimol, a GABAA receptor agonist, prevented the decreases in blood pressure and heart rate normally evoked by IL or POA activation. In addition, we found that intra-NTS microinjection of R(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine-methanol, a specific 5-HT2A receptor antagonist, did not affect the decreases in cardiovascular baseline parameters induced by IL or POA stimulation but prevented the facilitation of the aortic baroreflex bradycardia normally observed during IL (+65 and +60%) or POA (+70 and +69%) electrical and chemical stimulation, respectively. These results show that NTS 5-HT2A receptors play a key role in the enhancement of the cardiac response of the baroreflex but not in the changes in basal heart rate and blood pressure induced by IL or POA stimulation.
منابع مشابه
Role of nucleus tractus solitarius (NTS) 5-HT3 receptors in the defense reaction-induced inhibition of the aortic baroreflex in rats
CBaR: cardiac baroreflex response CPBG: 1-(m-chlorophenyl)-biguanide DMH: dorsomedial nucleus of the hypothalamus dPAG: dorsal part of the periaqueductal gray ECG: electrocardiogram HR: heart rate MBP: mean blood pressure NTS: nucleus tractus solitarius SBaR: sympathetic baroreflex response 3 ABSTRACT Different stressful conditions elicit a typical behaviour called the defense reaction. Our aim...
متن کاملFunctional interaction between nucleus tractus solitarius NK1 and 5-HT3 receptors in the inhibition of baroreflex in rats.
OBJECTIVE Previous data showed that in the nucleus tractus solitarius (NTS), 5-HT(3) receptors are critically involved in the inhibition of cardiac baroreceptor reflex response occurring during the defense reaction. Since stimulation of NTS NK(1) receptors has been found to inhibit the baroreflex bradycardia, we examined in this study whether this reflex response is inhibited during the defense...
متن کاملRole of nucleus tractus solitarius 5-HT3 receptors in the defense reaction-induced inhibition of the aortic baroreflex in rats.
Different stressful conditions elicit a typical behavior called the defense reaction. Our aim was to determine whether 5-HT3 receptors in the nucleus tractus solitarius (NTS) are involved in 1) the inhibition of the baroreflex bradycardia and 2) the rise in blood pressure, which are known to occur during the defense reaction. In urethane-anesthetized rats, the defense reaction was elicited by e...
متن کاملBaroreceptor reflex modulation by circulating angiotensin II is mediated by AT1 receptors in the nucleus tractus solitarius.
Circulating ANG II modulates the baroreceptor reflex control of heart rate (HR), at least partly via activation of ANG II type 1 (AT1) receptors on neurons in the area postrema. In this study, we tested the hypothesis that the effects of circulating ANG II on the baroreflex also depend on AT1 receptors within the nucleus tractus solitarius (NTS). In confirmation of previous studies in other spe...
متن کاملThe Effect of Nucleus Tractus Solitarius Nitric Oxidergic Neurons on Blood Pressure in Diabetic Rats
It has been shown that nitric oxide is synthesized in the central nervous system as well as in vascular endothelial cells. Recently, it was reported that nitric oxide was involved in central cardiovascular regulation, baroreflex modulation, and involved in a reciprocal release with excitatory amino acids in the nucleus tractus solitarii of rats. The purpose of the present study was to investiga...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- American journal of physiology. Regulatory, integrative and comparative physiology
دوره 291 4 شماره
صفحات -
تاریخ انتشار 2006