Differences in the neurochemical mechanisms of conditioning to stimuli of different modalities at the caudate nucleus level in rats

Microinjection of noradrenalin into the head of the caudate nucleus in rats did not affect the latent period of avoidance conditioning or muscle tone but inhibited motor activity, reduced the number of taps, and significantly increased the amplitude and latent period of the conditioned food-getting reflex. Local microinjection of serotonin into the neostriatum did not affect the latent period of the conditioned avoidance reflex and did not change the motor activity but it reduced the latent period and the number of taps in the conditioned food-getting response and increased its amplitude significantly. Dopamine inhibited the conditioned food and avoidance reflexes but significantly activated the spontaneous motor activity of the rats. The results are evidence of differences in the neurochemical mechanisms of conditioned reflexes to stimuli of different modalities closed at the caudate nucleus level in rats.