Intravenous administration of gamma aminobutyric acid (GABA) caused a dose-related (10-1000 βg/kg) hypotension and bradycardia in enflurane (Ethrane) anesthetized dogs. GABA also caused significant decreases in cardiac output, carotid artery blood flow, and in left and right ventricular stroke work indices. Pulmonary arterial and pulmonary wedge pressures were not affected. However, pulmonary vascular resistance was significantly increased after high doses of GABA. Muscimol (20 βg/kg, IV) produced effects similar to those caused by GABA. Blockade of GABA receptors with picrotoxin (1.5 mg/kg, IV) antagonized all effects of GABA and muscimol. Picrotoxin itself, as opposed to GABA, caused significant increases in mean arterial pressure, pulmonary arterial pressure, systemic vascular resistance, and pulmonary vascular resistance. Thus, it is suggested that blood-borne GABA or peripheral GABA-containing neurons may play a role in the control of blood pressure and other cardiopulmonary variables.
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