Effects of procaine, pentobarbital and halothane on synaptic transmission in the central nervous system.

Experiments were performed in the cuneate nucleus of decerebrate cats to study the effect of procaine, pentobarbital and halothane on pre- and postsynaptic structures. Pentobarbital and procaine, as well as other relevant compounds, were given by microiontophoresis using five-barrelled glass pipettes. Pentobarbital and halothane were also given systemically or by superfusion of the nucleus. Cuneate neurons were identified as relay units and interneurons, or according to their response to specific stimuli (touch, hair, joint). The results are consistent with the idea of multiple mechanisms of action responsible for the depression of synaptic transmission observed during the administration of anesthetics. Procaine depressed excitability of pre- and postsynaptic elements in a nonspecific way. Pentobarbital appeared more effective in depressing postsynaptic excitation. Halothane depressed synaptic transmission through the cuneate nucleus but had no significant effect on either pre- or postsynaptic structures.