Food-procuring behavior of rats under the conditions of chronic activation and blockade of the neostriatal dopaminergic system.

Using the technique of intracerebral microinjections, the features of food-procuring behavior (the realization of a situational instrumental conditioned reflex in a Skinner box) were investigated in rats in experiments under the conditions of a pharmacological influence on the dopaminergic system of the neostriatum. Amphetamine in a dose of 15 and 45 micrograms and haloperidol in a dose of 5 mg were injected daily over the course of three weeks bilaterally into the rostral division of the neostriatum. A amphetamine dose of 15 micrograms was ineffective, but a increase in motor hyperactivity, a behavioral stereotypy, and a substantial acceleration of food-procuring movements were observed against the background of the injection of 45 micrograms of amphetamine. Stimulation of the dopaminergic system of the neostriatum qualitatively altered the behavioral strategy in animals with an initially low level of realization of the reflex; this fostered a stable activation of the instrumental skill enduring even after the cessation of the microinjections. Chronic blockade of dopamine receptors by haloperidol induced the reverse effect.