Neurochemical mechanisms of participation of the caudate nuclei in food-getting behavior.

Abstract

1. Stimulation of acetylcholinergic structures of CN by microinjections of carbachol and neostigmine caused inhibition of the motor component of the conditioned food-getting reflex. The conditioned orienting reaction to acoustic stimuli and also the natural food reflex were not affected under these conditions. 2. Injection of carbachol and neostigmine into the head of CN led to a decrease, whereas injection of atropine led to an increase in amplitude of the late components of EP in the motor and somatosensory areas of the cortex to conditioned acoustic stimuli. 3. Stimulation of the dopaminergic structures of CN by apomorphine caused facilitation of the food-getting conditioned reflex, whereas inhibition of dopaminergic structures of CN by haloperidol led to inhibition of this reflex. 4. Microinjections of dopamine and dopaminotropic agents into the head of CN had a much weaker effect on the food-getting conditioned reflex than neurochemical action on the acetylcholinergic structures of this nucleus. 5. Analysis of EP in the motor and somatosensory cortex in response to conditioned acoustic stimuli after administration of apomorphine and haloperidol revealed no antagonism between the acetylcholinergic and dopaminergic systems of CN. Apomorphine, like acetylcholinomimetics, caused a decrease, whereas haloperidol caused an increase in amplitude of the late components of EP.