A receptors in the NTS modulate depression of carotid baroreflex induced by intracerebroventricular injection of histamine in rats / 中国应用生理学杂志

<p><b>AIM</b>To investigate the roles of alpha1 and alpha2 receptors in the nucleus tractus solitarius (NTS) in the carotid baroreflex (CBR) resetting induced by the intracerebroventricular injection (ICV) of histamine (HA).</p><p><b>METHODS</b>The left and right carotid sinus regions were isolated from the systemic circulation in 25 Sprague-Dawley rats anesthetized with pentobarbital sodium. The intracarotid sinus pressure (ISP) was altered in a stepwise manner. ISP-mean arterial pressure (MAP) relationship curve and its characteristic parameters were constructed by fitting to the logistic function with five parameters. The changes in CBR performance induced by ICV HA and the effects of pretreatment with alpha1 or alpha2 receptor antagonist into the NTS on the responses of CBR to HA were examined.</p><p><b>RESULTS</b>ICV HA (60 micromol x L(-1) in 5 microl) significantly shifted the ISP-MAP relationship curve upwards (P < 0.05) and moved the middle part of ISP-Gain relationship curve downwards (P < 0.05), and reduced the MAP range and maximum gain (P < 0.05). The pretreatment with phenoxybenzamine (PBZ, a selective antagonist of alpha1 receptor, 3 micromol x L(-1) in 500 nl) or yohimbine (YOH, a selective antagonist of alpha2 receptor, 2.5 micromol x L(-1) in 500 nl) into the NTS could obviously intensify the above-mentioned changes in CBR performance induced by HA, but the intensive effect of PBZ was less remarkable than that of YOH (P < 0.05).</p><p><b>CONCLUSION</b>The intracerebroventricular administration of HA results in a rapid resetting of CBR and a decrease in reflex sensitivity, and the functions of alpha1 and alpha2 receptors in the NTS might weaken CBR resetting induced by ICV HA. Furthermore, alpha2 receptor in the NTS might play an more important role in modulating the responses of CHR to HA.</p>

H(1) and H(2) receptors in the locus ceruleus are involved in the intracerebroventricular histamine-induced carotid sinus baroreceptor reflex resetting in rats / 神经科学通报·英文版

Objective To investigate the role of H(1) and H(2) receptors in the locus ceruleus (LC) in carotid sinus baroreceptor reflex (CSR) resetting induced by intracerebroventricular (i.c.v.) injection of histamine (HA). Methods The left and right carotid sinus regions were isolated from the systemic circulation in 18 male Sprague-Dawley rats anesthetized with pentobarbital sodium. The intracarotid sinus pressure (ISP) was altered in a stepwise manner in vivo. ISP-mean arterial pressure (MAP) relationship curve and its characteristic parameters were constructed by fitting to the logistic function with five parameters. The changes in CSR performance induced by i.c.v. HA and the effects of pretreatment with H(1) or H(2) receptors selective antagonist, chlorpheniramine (CHL) or cimetidine (CIM) into the LC, on the responses of CSR to HA were examined. Results I.c.v. HA (100 ng in 5 mu l) significantly shifted the ISP-MAP relationship curve upwards (P < 0.05) and obviously decreased the value of the reflex parameters such as MAP range and maximum gain (P < 0.05), but increased the threshold pressure, saturation pressure and ISP at maximum gain (P < 0.05). The pretreatment with CHL (0.5 mu g in 1 mu l) or CIM (1.5 mu g in 1 mu l) into the LC could obviously attenuate the changes mentioned above in CSR performance induced by HA, but the alleviative effect of CIM was less remarkable than that of CHL (P < 0.05). Respective microinjection of CHL or CIM alone into the LC with the corresponding dose and volume did not change CSR performance significantly (P > 0.05). Conclusion Intracerebroventricular administration of HA results in a rapid resetting of CSR and a decrease in reflex sensitivity, and the responses of CSR to HA may be mediated, at least in part, by H(1) and H(2) receptors activities in the LC, especially by H(1) receptors. Moreover, the effects of the central HA on CSR might be related to a histaminergic descending pathway from the hypothalamus to LC.

A receptors in the locus ceruleus involved in attenuating the intracerebroventricular histamine-induced carotid baroreflex resetting in rats / 中国应用生理学杂志

<p><b>AIM</b>To investigate the effects of alpha1 and alpha2 receptors in the locus ceruleus (LC) on carotid baroreflex (CBR) resetting induced by intracerebroventricular injection (ICV) of histamine (HA).</p><p><b>METHODS</b>The left and right carotid sinus regions were isolated from the systemic circulation in 23 Sprague-Dawley rats anesthetized with pentobarbital sodium. The intracarotid sinus pressure (ISP) was altered in a stepwise manner. ISP-mean arterial pressure (MAP) relationship curve and its characteristic parameters were constructed by fitting to the logistic function with five parameters. The changes in CBR performance induced by ICV HA and the effects of pretreatment with alpha1 or alpha2 receptor antagonist into the LC on the responses of CBR to HA were examined.</p><p><b>RESULTS</b>ICV HA (60 micromol x L(-1) in 5 microl) significantly shifted the ISP-MAP relationship curve upwards (P < 0.05) and reduced the MAP range and maximum gain (P < 0.05). The pretreatment with phenoxybenzamine (PBZ, a selective antagonist of alpha1 receptor, 3 micromol x L(-1) in 500 nl) or yohimbine (YOH, a selective antagonist of alpha2 receptor, 2.5 micromol x L(-1) in 500 nl) into the LC could obviously intensify the above-mentioned changes in CBR performance induced by HA, but the intensive effect of PBZ was less remarkable than that of YOH (P < 0.05).</p><p><b>CONCLUSION</b>The intracerebroventricular administration of HA results in a rapid resetting of CBR and a decrease in reflex sensitivity, and the functions of alpha1 and alpha2 receptors in the LC may attenuate CBR resetting induced by ICV HA. Furthermore, alpha2 receptor in the LC might play a more important role in regulating the responses of CBR to HA.</p>

Histaminergic receptor in the NTS involved in inhibition of carotid baroreflex induced by intracerebroventricular injection of HA in rats / 中国应用生理学杂志

<p><b>AIM</b>To explore the role of histaminergic receptors in the nucleus tractus solitarius (NTS) in the responses of carotid baroreflex (CBR) performance to the intracerebroventricular (ICV) injection of histamine (HA).</p><p><b>METHODS</b>The left and right carotid sinus regions were isolated from the systemic circulation in 18 Wistar rats anesthetized with pentobarbital sodium. The intracarotid sinus pressure (ISP) was altered in a stepwise manner. ISP-mean arterial pressure (MAP) relationship curve and its characteristic parameters were constructed by fitting to the logistic function with five parameters. We observed the changes in CBR performance induced by ICV HA and the effects of pretreatment with HA receptors antagonists into the NTS on the responses of CBR to HA.</p><p><b>RESULTS</b>ICV injection of HA (100 ng) significantly shifted the ISP-MAP relationship curve upwards and moved the middle part of ISP Gain relationship curve downwards, and reduced the MAP range and maximum gain (Gmax), but increased the threshold pressure (TP), saturation pressure(SP) and ISP at Gmax (ISP(Gmax)). The pretreatment with H1 or H2 receptors antagonist, chlorpheniramine (CHL, 0.5 microg) or cimetidine (CIM, 1.5 microg) into the NTS, could obviously diminish the above-mentioned changes in CBR performance induced by HA, but the effect of CIM was less remarkable than that of CHL.</p><p><b>CONCLUSION</b>The intracerebroventricular administration of HA results in a rapid resetting of CBR and a decrease in reflex sensitivity, and the histaminergic receptors in the NTS (H1 and H2 receptors), especially H1 receptors might play an important role in the responses of CBR to HA, and furthermore, the effects of the central HA on CBR might be related to a histaminergic descending pathway from the hypothalamus to NTS.</p>

Effects of central histaminergic receptor activation on carotid sinus baroreceptor reflex resetting in stressed rats / 生理学报

To determine the effect of stress on carotid sinus baroreceptor reflex (CSR) and whether or not central histaminergic receptors modulate the CSR under stress, the characteristics of CSR were analyzed by using an isolated carotid sinus preparation in Wistar rats. Animals were divided into two groups at random: unstressed group (n=42) and stressed group (n=41). According to the site of microinjection of histaminergic receptor antagonists, each group was subdivided into a group of intracerebroventricular injection (i.c.v.) and a group of microinjection into the nucleus of the solitary tract (NTS). The volume of injection into the lateral cerebroventricle and NTS was 5 microl and 1 micro1, respectively. Stressed groups were subjected to unavoidable electric foot-shock twice daily for a week, each session of foot-shock lasted 2 hours. The left and right carotid sinus regions were isolated from the systemic circulation under anesthesia with pentobarbital sodium in all rats. The intracarotid sinus pressure (ISP) was altered in a stepwise manner to trigger CSR from 0 to 280 mmHg at every step of 40 mmHg and 4 s, and then returned to 0 mmHg in similar steps. ISP and mean arterial pressure (MAP) were recorded simultaneously. ISP-MAP relationship curve was constructed by fitting to the logistic function with five parameters. The CSR parameters and the ISP-MAP relationship curve were separately compared statistically. The main results obtained are as follows. (1) Stress significantly shifted the ISP-MAP relationship curve upwards and obviously moved the middle part of ISP-Gain relationship curve downwards, and decreased the value of the MAP range and maximum gain (G(max)), but increased the threshold pressure (TP), saturation pressure (SP), set point and ISP at G(max) (ISP(Gmax)). (2) I.c.v. of H1 receptor antagonist chlorpheniramine (CHL, 5 microg) or H2 receptor antagonist cimetidine (CIM, 15 g) significantly diminished the above-mentioned changes in CSR performance induced by stress; the alleviative effect of CIM was less remarkable than that of CHL. The responses of CSR in stressed rats to H(1) or H(2) receptor antagonists generally occurred 20 min after the administration and lasted approximately for 15 min. (3) After microinjection of CHL (0.5 microg) or CIM (1.5 microg) into the NTS, the responses of CSR in stressed groups were similar to those after i.c.v. injection of CHL or CIM. (4) However, microinjection of CHL or CIM into the lateral cerebroventricle or the NTS could not completely abolish the stress-induced changes in CSR. These findings suggest that stress results in a resetting of CSR, a decrease in reflex sensitivity. The stress-induced changes in CSR may be mediated, at least in part, by activating the brain histaminergic system. The central histaminergic receptors (H(1) and H(2) receptors) may play an important role in the resetting of CSR under stress. The descending histaminergic pathway from the hypothalamus to NTS may be involved in these effects.

The role of L-type Ca2+ current and reverse mode Na+ -Ca2+ exchange in activation of excitation-contraction coupling in guinea-pig ventricular myocytes / 中国应用生理学杂志

<p><b>AIM</b>To study and compare the excitation-contraction coupling triggered by L-type calcium current and by reverse-mode Na/Ca exchange during depolarizing steps in single guinea-pig ventricular myocytes.</p><p><b>METHODS</b>Whole-cell membrane-potential, membrane-current and cell-shortening data were simultaneously acquired during whole-cell voltage clamp protocols. Voltage clamp pulses elicited ICa(L) at + 10 mV, + 50 mV, + 100 mV and evoked contractions in myocytes superfused with Tyrode's solution at 35 degrees C.</p><p><b>RESULTS</b>The greater the inhibition of I(Ca(L)), the more likely contractions would be abolished at +10 mV test potential. There was a correlation between them. At potential positive to + 50 mV, contractions were partially suppressed by Nif 100 micromol/L or Nif 30 micromol/L plus Cd2+30 micromol/L. The residual contraction was significantly delayed in onset. At +100 mV test potential, contractions were delayed in onset compare to + 50 mV and resistant to Nif 100 micromol/L or Nif 30 micromol/L plus Cd2+30 micromol/L. The residual contraction was completely blocked by Ni2+ at + 50 mV and + 100 mV.</p><p><b>CONCLUSIONS</b>I(Ca(L)) is the major trigger for excitation-contraction coupling. Na/Ca exchange modulates excitation-contraction coupling as both reverse and forward mode.</p>

Effect of intracerebroventricular injection of histamine on carotid sinus baroreceptor reflex in anesthetized rats and its mechanism / 生理学报

The changes in carotid sinus baroreceptor reflex (CSR) performance induced by intracerebroventricular injection (i.c.v.) of histamine (HA) were investigated. The effects of pretreatment with HA receptors antagonists into the cerebroventricle or nucleus of solitary tract (NTS) on the responses of CSR to HA were also examined. Intracarotid sinus pressure (ISP)-mean arterial pressure (MAP) relationship curve was constructed by fitting to the logistic function with five parameters in 50 Wistar rats anesthetized with pentobarbital sodium. The left and right carotid sinus regions were isolated from the systemic circulation and the ISP was altered in a stepwise manner. The main results obtained are as follows. (1) i.c.v. injection of HA (100 ng) significantly shifted the ISP-MAP relationship curve upwards and moved the middle part of ISP-Gain relationship curve downwards, and reduced the MAP range and maximum gain (G(max)), but increased the threshold pressure (TP), saturation pressure (SP) and ISP at G(max) (ISP (Gmax)). (2) The pretreatment with H(1) or H(2) receptors antagonist, chlorpheniramine (CHL, 5 microg) or cimetidine (CIM, 15 microg), could obviously diminish the above-mentioned changes in CSR performance induced by HA, but the effect of CIM was less remarkable than that of CHL. (3) The pretreatment with both CHL and CIM (5 microg and 15 microg) at the same time abolished the responses of CSR performance to HA completely. (4) After microinjection of CHL (0.5 microg) or CIM (1.5 microg) into the NTS, the responses of CSR to HA were similar to those after i.c.v. CHL or CIM, but the change in TP was significantly decreased. These findings suggest that the intracerebroventricular administration of HA results in a rapid resetting of CSR and a decrease in reflex sensitivity. The response of CSR to HA might be mediated by both central H(1) and H(2) receptors, especially by H(1) receptors. The effects of the central HA on CSR might be related to a histaminergic descending pathway from the hypothalamus to NTS. It is suggested that the HA receptors in the NTS play an important role in the responses of CSR to HA.