The bradycardic and hypotensive responses to serotonin are reduced by activation of GABA A receptors in the nucleus tractus solitarius of awake rats

Autor(es)

J.C. Callera ^[1] ; E. Colombari ; L.A. De Luca Jr. ^[3] ; J.V. Menani ^[4]

Afiliação do(s) autor(es)

^[1] Universidade Estadual Paulista. Faculdade de Odontologia. Departamento de Ciências Básicas - Brasil

^[3] Universidade Estadual Paulista. Faculdade de Odontologia. Departamento de Fisiologia e Patologia - Brasil

^[4] Universidade Estadual Paulista. Faculdade de Odontologia. Departamento de Fisiologia e Patologia - Brasil

• Tipo de documento: Artigo Científico
• Fonte: Brazilian Journal of Medical and Biological Research; v. 38, n. 7, p. 1123-1131, 2005-07-00.

Resumo

We investigated the effects of bilateral injections of the GABA receptor agonists muscimol (GABA A) and baclofen (GABA B) into the nucleus tractus solitarius (NTS) on the bradycardia and hypotension induced by iv serotonin injections (5-HT, 2 µg/rat) in awake male Holtzman rats. 5-HT was injected in rats with stainless steel cannulas implanted bilaterally in the NTS, before and 5, 15, and 60 min after bilateral injections of muscimol or baclofen into the NTS. The responses to 5-HT were tested before and after the injection of atropine methyl bromide. Muscimol (50 pmol/50 nl, N = 8) into the NTS increased basal mean arterial pressure (MAP) from 115 ± 4 to 144 ± 6 mmHg, did not change basal heart rate (HR) and reduced the bradycardia (-40 ± 14 and -73 ± 26 bpm at 5 and 15 min, respectively, vs -180 ± 20 bpm for the control) and hypotension (-11 ± 4 and -14 ± 4 mmHg, vs -40 ± 9 mmHg for the control) elicited by 5-HT. Baclofen (12.5 pmol/50 nl, N = 7) into the NTS also increased basal MAP, but did not change basal HR, bradycardia or hypotension in response to 5-HT injections. Atropine methyl bromide (1 mg/kg body weight) injected iv reduced the bradycardic and hypotensive responses to 5-HT injections. The stimulation of GABA A receptors in the NTS of awake rats elicits a significant increase in basal MAP and decreases the cardiac Bezold-Jarisch reflex responses to iv 5-HT injections. (AU)

• Processo FAPESP: 01/06246-4 - Possivel interacao entre receptores gabaergicos e serotonergicos 5-ht3 do nts no controle da pressao arterial e no reflexo bezold-jarisch.
• Beneficiário: João Carlos Callera
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado