This study examined the dose-dependent effects of acute ethanol on rec
urrent inhibitory mechanisms of hippocampal CA1 neurons in anesthetize
d rats. The effects of micropressure-ejected GABAergic compounds were
studied on evoked field responses and recurrent inhibition of CA1 pyra
midal neurons. None of the systemic doses of ethanol examined altered
recurrent inhibition of CA1 neurons. In contrast, local application of
both GABAa and GABAb compounds produced clear changes in evoked field
responses and blocked recurrent inhibition. These results suggest tha
t (a) recurrent inhibition in the CA1 region in vivo is resistant to t
he effects of ethanol, and (b) both GABAergic receptor subtypes modula
te recurrent inhibition in the CA1 region in vivo.