Paper Information

Title: 

VASOPRESSIN MEDIATES THE CARDIOVASCULAR EFFECTS OF GABAERGIC SYSTEM IN THE BED NUCLEUS OF THE STRIA TERMINALIS

Type: SPEECH
Author(s): HATAM MASOUMEH*,NASIMI A.,KHARAZMI F.
 
 *DEPARTMENT OF PHYSIOLOGY, ISFAHAN UNIVERSITY OF MEDICAL SCIENCES, ISFAHAN
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2009Volume 19
 
 
Abstract: 

The bed nucleus of the stria terminalis (BST) is a part of the limbic system. Previous study showed inhibition of GABA A receptor increased blood pressure and heart rate. This study was performed to find the possible mechanisms and circuitry that mediate these responses. Experiments were done in 39 urethane-anesthetized male rats. Femoral artery and vein were cannulated for recording the blood pressure and heart rate and drug injection respectively. Trachea was cannulatted to ease ventilation. Bicuculline unilaterally microinjected into the BST using micropipette. The maximum changes of mean arterial pressure (MAP) heart rate (HR) were compared with the preinjection values using paired t- test. Injection of bicuculline methiodide (BMI, 100 pmol/100 nl), a GABAA antagonist, caused significant increase in the MAP (41.3 ± 5.1 mmHg) as well as in the HR (33.2 ± 5.6 beats/min). Administration (i.v.) of the muscarinic receptor blocker, homatropine methyl bromide had no affect on the magnitude of mean arterial pressure or heart rate responses to BMI. This suggests that the parasympathetic system is not involved in these responses. But administration (i.v.) of the the nicotinic receptor blocker, hexamethonium bromide had no effect on the magnitude of mean arterial pressure response but abolished heart rate response to BMI. This suggests that the sympathetic system is involved in the bradycardic effect of GABA. On the other hand, administration (i.v.) of a selective vasopressin V1 receptor antagonist abolished the pressor effect of BMI, which indicates that the GABAergic system of the BST decrease the arterial pressure via tonic inhibition of vasopressin release. In summary, we demonstrated, for the first time, inhibition of GABAA, receptors increase blood pressure and heart rate via; tonically inhibit vasopressin release and sympathetic outflow to the heart.

 
Keyword(s): BED NUCLEUS OF THE STRIA TERMINALIS, GABA, BLOOD PRESSURE, HEART RATE, VASOPRESSIN
 
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