Document Detail

The bradycardic and hypotensive responses to serotonin are reduced by activation of GABAA receptors in the nucleus tractus solitarius of awake rats.
MedLine Citation:
PMID:  16007284     Owner:  NLM     Status:  MEDLINE    
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 microg/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.
J C Callera; E Colombari; L A De Luca; J V Menani
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-07-04
Journal Detail:
Title:  Brazilian journal of medical and biological research = Revista brasileira de pesquisas médicas e biológicas / Sociedade Brasileira de Biofísica ... [et al.]     Volume:  38     ISSN:  0100-879X     ISO Abbreviation:  Braz. J. Med. Biol. Res.     Publication Date:  2005 Jul 
Date Detail:
Created Date:  2005-07-11     Completed Date:  2006-01-09     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8112917     Medline TA:  Braz J Med Biol Res     Country:  Brazil    
Other Details:
Languages:  eng     Pagination:  1123-31     Citation Subset:  IM    
Departamento de Ciências Básicas, Faculdade de Odontologia, Universidade Estadual Paulista, Araçatuba, SP, Brasil.
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MeSH Terms
Baclofen / pharmacology
Blood Pressure / drug effects*
Bradycardia / physiopathology
GABA Agonists / pharmacology*
Heart Rate / drug effects*
Hypotension / physiopathology
Muscimol / pharmacology
Rats, Sprague-Dawley
Receptors, GABA-A / drug effects*,  physiology
Serotonin / administration & dosage,  pharmacology*
Solitary Nucleus / drug effects*,  physiology
Reg. No./Substance:
0/GABA Agonists; 0/Receptors, GABA-A; 1134-47-0/Baclofen; 2763-96-4/Muscimol; 50-67-9/Serotonin

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