MECHANISMS OF SYNAPTIC TRANSMISSION IN THE CUNEATE NUCLEUS

Abstract

Previous investigations have shown the important role of presynaptic inhibition in the cuneate nucleus of cats anaesthetized with intraperitoneal sodium pentobarbital,but it is now shown by direct electrical testing that a prolonged depression of cuneate neuron excitability is produced by a cutaneous afferent volley or a contralateral cortical stimulation, an effect which is attributed to a postsynaptic inhibitory action. Direct evidence of this postsynaptic inhibitory action by afferent volleys was obtained by intracellular recording of typical IPSPs [inhibitory post-synaptic potential] from cuneate neurons, some being brief (20 msec) and others of long duration (about 200 msec). Investigation was also made of the presynaptic inhibitory action in depressing the presynaptic depolarization produced by afferent volleys or by contralateral cortical stimulation. There is a general discussion of the roles of these 2 types of inhibition in the normal func -tioning of the cuneate nucleus.