Effects of blockade of dopamine d(1)/d (2) receptors on the single and network activity of neurons in the frontal and visual cortex and behavior in cats.
ABSTRACT Results obtained at the single (cell discharge) and network levels of activity of cells in the frontal and visual cortex in animals with different types of behavior identified the characteristics of the activity of these structures in normal conditions and after local administration of blockers of dopaminergic D(1)/D(2) receptors (SCH23390 and raclopride) into the nucleus accumbens and frontal cortex. In conditions of long-latency responses, the mean neuron activity frequency in the frontal cortex was increased significantly by blockers, while that in the visual cortex decreased as compared with the neuron activity frequency in normal conditions, which suggests that dopaminergic deficiency has different effects on functionally distinct cortical zones. The network activity of the same cells decreased in the presence of blockers both in the visual cortex and between neurons in the visual and frontal areas of the cortex, which was apparent as a decrease in the number of interneuronal interactions. The network activity of cells in the frontal cortex showed no change in these conditions. In "missed" reflexes, the discharge and network activity showed no change in the frontal cortex in the presence of blockers, while there was a decrease in the visual cortex. The mean neuron discharge frequency in interneuronal interactions was found to be significantly greater in these structures in both normal conditions and in the presence of blockers during long-latency conditioned responses as compared with missed conditioned responses. These results suggest differences in the modulation of the network activity of these cortical zones by the brain dopaminergic system during performance of directed behavior, which is apparent as blocker sensitivity in the cortical projections of the conditioned stimulus (visual cortex) and the visual-frontal networks formed during training.