Biphasic actions of pentobarbital on synaptic transmission.

The effects of pentobarbital were studied on synaptic transmission in the rat hippocampal slice preparation. Low concentrations of pentobarbital (0.04 - 0.1 mM) produced an increase in the Schaffer collateral to CA 1 evoked EPSP and population field potential amplitudes. Higher concentrations of pentobarbital (0.2 - 1.0 mM) produced depression of field potential amplitudes. Pentobarbital altered synaptic transmission by affecting both pre- and post-synaptic functions. Analysis of input/output curves suggest the presynaptic site is most sensitive.