[Effect of dopamine on activity of brain sensory-motor cortex neurons during conditioned reflex]

A changes of background and evoked activity of deep cortical layers neurons and latency of the movement in the response to the conditioned stimuli were investigated in cats chronical experiments during microelectrode iontophoretic local aplication of dopamine, its antagonists and antagonists ofglutamatergic and gabaergic transmission. It was shown, that application of dopamine and others synapticaly active substances near soma of pyramidal neurons moderately increased their background and evoked activity and did not sygnificantly change their latency. Application of dopamine antagonists sulpiride and SCH 23390 depressed the background and evoked impulse activity and increased the latency of neuronal reaction and conditioned movements. These effects were completely removed by the aplication of the same antagonists together with dopamine. Dopamine removed the depressing influence on the background and evoked impulse activity and latency of the conditioned reflexes evoked by application of antagonists of glutamate ionotropic and metabotropic transmission (AP-4 and MCPG). The same stabilized influences were evoked by the iontophoretic application of GABA antagonist bicuculline. It was concluded that effects of dopamine are connected with its local inhibitory influences on the inhibitory interneurons and their synaptic endings on soma of pyramidal neurons.