Effects of peripherally administered GABA and other amino acids on cardiopulmonary responses in anesthetized rats and dogs.

Intravenously administered GABA (1.0-1000 micrograms/kg) induced hypotension, bradycardia and tachypnea in both dogs and rats. The increased respiratory rate was not caused by changes in blood pH, pCO2, or pO2. None of the effects of GABA were modified by the following agents: propranolol, atropine, diphenhydramine, or hexamethonium. Taurine, glycine, beta-alanine, glutamic acid and aspartic acid at doses of 1000 micrograms/kg, i.v., had no significant effects on any of the variables measured. Since these doses of GABA probably do not cross the blood-brain barrier, it is postulated that the observed effects of GABA may be due to direct actions on vascular, cardiac and lung tissue. The exact site of GABA action in the periphery remains to be elucidated.