A barbiturate induced intensification of the inhibitory potential in slices of guinea‐pig olfactory cortex.

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Abstract
The effect of barbiturates on membrane constants and synaptic potentials of neuron in the isolated guinea pig olfactory cortex slice was studied. Normally, a long depolarizing IPSP [inhibitory postsynaptic potential] follows the E[excitatory]PSP. Pentobarbitone (0.1 mM) produced a 10-fold increase in the duration of the high conductance phase of this IPSP. The IPSP was potentiated increasingly with higher barbiturate concentrations from 0.02-1.0 mM pentobarbitone and 0.2-5 mM phenobarbitone. The resting membrane conductance, the initial phase of the EPSP and the threshold for the action potential were unaffected at lower concentrations. The highest barbiturate doses increased the resting membrane conductance. This was associated with a depolarization of about 14 mV maximally and resulted in smaller synaptic potentials. The effect was probably generated by the same mechanism as the IPSP. Barbiturates apparently have a primary action on prolonging inhibition rather than a depression in the excitatory potential.