Central neurophysiologic mechanisms of the regulation of inhibition

The neuronal populations of the cuneate nucleus of the midbrain, the medial parabrachial nucleus, the median and magnus nuclei of the raphé, the electrical and local chemical stimulation of which elicits the inhibition of the motor activity of animals, were determined in chronic experiments on freely-moving white male mongrel rats. It was established that when each of the enumerated regions of the brain are stimulated electrically in other zones which elicit motor inhibition, multineuronal responses with a latent period of less than 2.5 msec were recorded. At the same time, multidirectional bilateral changes in muscle tone of the flexors and extensors of the hind limbs are observed in sodium ethaminal anesthetized and unanesthetized animals. The electrolytic destruction of the inhibitory zones of the median raphé nucleus and raphé nucleus magnus blocks the motor inhibition elicited by electrical stimulation of the cuneate nucleus of the midbrain and the medial parabrachial nucleus.