THE EFFECT OF INTRAVENOUS ADMINISTRATION OF GABA AND BRAIN EXTRACTS ON BLOOD PRESSURE IN THE RAT

1. A rat bioassay was used to study pressor substances in brain extracts. 2. A compound with pressor activity in pentolinium-treated rats was extracted from brain, purified using Dowex, Sephadex electrophoresis and identified as γ-aminobutyric acid (GABA) by HPLC and mass spectrometry. 3. Intravenous GABA (1-5 μg) or brain extracts caused a dose dependent decrease in blood pressure in pentobarbitone-anaesthetized rats. 4. After ganglion blockade with pentolinium (2 mg/kg subcutaneously), GABA or brain extracts cause a dose dependent increase in rat blood pressure. 5. This pressor effect is reduced by α- and β-blockers (intravenous phentol-amine, 0-5 mg/kg and propranolol, 005 mg/kg). 6. It is concluded that GABA causes a fall in blood pressure by a central mechanism and ganglion blockade unmasks a pressor effect.