GABA and behavioral inhibition in the neonatal rat pup.

The effects of the GABA agonist muscimol and GABA antagonist picrotoxin were examined in 3-4-day-old deprived rat pups under conditions of low (absence of milk) and high (milk presence) activity baselines. A low dose of muscimol was observed to have activating effects under low baseline conditions, whereas higher doses of muscimol were observed to depress milk-induced activity and mouthing. Picrotoxin treatment was observed to increase activation of these neonates under both baseline conditions. Taken together, these results provide evidence for a functional GABAergic inhibition of behavior in the neonate.