The participation of cholinergic systems of the nucleus accumbens in the differentiation of acoustic signals in dogs.

The influence of microinjections of the choline agonist, (carbacholine 0.05-0.1 microgram), into the nucleus accumbens (Acc) of the right and left hemispheres on the realization of an instrumental defense reflex associated with the maintenance of a specific posture, and on the differentiation of acoustic signals in a defense situation, was studied in chronic experiments in five dogs. It was demonstrated that the injection of fairly small doses of carbacholine (CbCh) into the Acc of the left and right hemispheres improves the differentiation of acoustic signals in the defense situation. The introduction of fairly small doses of CbCh also improves the values of the criteria of the execution of the instrumental defense reaction associated with the maintenance of a specific posture. The changes observed are prolonged in character. Analysis of the motoric components of the instrumental responses made it possible to evaluate objectively the contribution of the motor and sensory mechanisms to those changes which were elicited by the microinjections of CbCh into the Acc, and to reach conclusion regarding an important role of the cholinergic system of the nucleus accumbens in sensory processes associated with the initiation and realization of instrumental responses to defense and differential signals, and especially in the regulation of attention to significant stimuli.