Navegando por Autor "Bonagamba, Leni Gomes Heck"
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Item Neurotransmission of the Bezold-Jarisch reflex in the nucleus tractus solitarii of sino-aortic deafferentated rats.(1997) Chianca Júnior, Deoclécio Alves; Bonagamba, Leni Gomes Heck; Machado, Benedito HonórioThe Bezold-Jarisch _B-J. reflex was activated by serotonin _5-HT, i.v.. before and 10 min after bilateral microinjection of increasing doses of kynurenic acid, a non-selective antagonist of excitatory amino acid _EAA. receptors, into the commissural nucleus tractus solitarii _NTS. of sino-aortic deafferentated _SAD. and sham-operated _SO. unanesthetized rats. Increasing doses of kynurenic acid produced a dose-dependent blockade of the bradycardic and hypotensive responses to B-J reflex activation in both SO _from 0.1 to 10.0 nmolr100 nl. and SAD _from 0.1 to 2.0 nmolr100 nl.. Comparison of the effect of kynurenic acid on the hypotension and bradycardic dose–response curves showed a significant difference between SO and SAD rats, indicating that smaller doses of kynurenic acid are required in SAD rats than in SO rats to block the neurotransmission of the B-J reflex in the NTS. The data also showed that bilateral microinjection of kynurenic acid into the NTS at doses of 0.5 _131"7 vs. 115"8 mmHg. and 2.0 nmolr100 nl _140"11 vs. 116"9 mmHg. produced an acute and significant increase in the basal mean arterial pressure of SAD rats similar to that observed with the same doses in SO rats, which was back to control values 5–10 min later. The increase in basal mean arterial pressure immediately after kynurenic acid microinjection into the NTS of SAD rats suggests that in the absence of the arterial baroreceptors, the B-J reflex plays an important role in the autonomic regulation of the circulation. The data also show different dose–response curves for hypotension and bradycardia in response to B-J reflex activation in SAD than in SO rats in the presence of increasing doses of kynurenic acid into the NTS, indicating that the neurotransmission of the B-J reflex in the NTS of SAD rats is more sensitive to the blockade of the EAA receptors than in SO rats.Item NMDA receptors in NTS are involved in the bradycardic but not in the pressor response of chemoreflex.(1995) Haibara, Andréa Siqueira; Colombari, Eduardo; Chianca Júnior, Deoclécio Alves; Bonagamba, Leni Gomes Heck; Machado, Benedito HonórioActivation of carotid chemoreceptors with intravenous potassium cyanide (KCN) produces increases in arterial pressure, bradycardia, and tachypnea. In the present study, we activated carotid chemoreceptors with KCN and the neurotransmission of the chemoreceptor reflex into the commissural nucleus tractus solitarii (NTS) was blocked with phosphonovaleric acid @P-5), an N-methyl-D-aspartate (NMDA)-selective antagonist. The aim of this study was to evaluate the involvement of NMDA receptors in the cardiovascular and respiratory responses produced by chemoreceptor activation in unanesthetized rats. The pressor response to KCN was not changed after microinjection of three different doses of AP-5 into the NTS, whereas the bradycardic response was reduced in a dosedependent manner. The increase in respiratory frequency in response to carotid chemoreceptor activation was also not affected by AP-5 microinjected into the NTS. The data indicate that the activation of the cardiovagal component of the chemoreflex in the commissural NTS is mediated by NMDA receptors, whereas pressor and ventilatory responses are not.