.BETA.-Phenyl-.BETA.-Alanine Prevents the Activation of Vagal Efferent Discharges Evoked by Baclofen and GABA in Rats.

The effects of DL-beta-phenyl-beta-alanine (BPBA) on vagal efferent discharges elicited by gamma-aminobutyric acid (GABA) and baclofen were investigated in rats. When given alone, BPBA (40 mg/kg, i.v.) caused no significant change in vagal nerve response and did not elicit any convulsions. Pretreatment with BPBA (40 mg/kg, i.v.) resulted in 70% and 80% reductions in the vagal efferent discharges induced by GABA (400 mg/kg, i.v.) and baclofen (4 mg/kg, s.c.), respectively. The present results suggest that BPBA may be a novel GABA antagonist with respect to vagal activation mechanisms in the CNS.