Effects of Intra-accumbens Administration of Dopamine Agonists on Stress-induced Behavioural Deficit

Abstract
The effect of post-footshock injections of (+)-amphetamine, the selective D2-receptor agonist quinpirole (LY 171555), and the D2-receptor antagonist metoclopramide, into the nucleus accumbens, on the formation of the open field deficit, has been studied in rats. Microinjections of (+)-amphetamine (10 μg) stimulated rat locomotor activity tested 5 min later, while quinpirole (10 μg) significantly inhibited animal motility in the test. The open field behaviour was not changed 24 h after injection of either drug. Amphetamine applied immediately after inescapable footshock did not modify stress-induced locomotor depression, when the rats' behaviour was examined 24 h later. On the other hand, post-shock injections of quinpirole significantly attenuated the long-term effects of the stressor, in the open field. Metoclopramide (10 μg) inhibited rat locomotor activity 5 min, but not 24 h, after local injection. Administration of a solution containing both quinpirole (10 μg) and metoclopramide (1 μg) decreased motor activity of unstressed rats to a smaller degree than did quinpirole (10 μg) alone. Post-footshock injection of metoclopramide did not affect stress-induced hypomotility. It is concluded that the present data support the hypothesis that local depletion of brain dopaminergic stores causes some behavioural effects of stressors.

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