Differentiation of the dopamine mechanisms mediating stereotyped behaviour and hyperactivity in the nucleus accumbens and caudate-putamen

Abstract

Abstract A number of dopamine agonists were applied intracerebrally to the nucleus accumbens and caudate-putamen of rat in an attempt to differentiate the dopamine mechanisms in these nuclei which mediate hyperactivity and stereotyped behaviour. The major effect of dopamine was to induce hyperactivity from the nucleus accumbens and stereotypy from the caudate-putamen; N-n-propyl-norapomorphine induced hyperactivity and stereotypy from the nucleus accumbens whilst apomorphine induced a marked stereotypy from the caudate-putamen, modest stereotypy from the nucleus accumbens and no hyperactivity. In contrast to apomorphine, 2-(NN-dipropyl)amino-5,6-dihydroxy TN‡ induced a more marked stereotypy from the nucleus accumbens and, again, no hyperactivity. The major effect of 2-(NN-diethyl)amino-5,6-dihydroxy TN was to cause an intense hyperactivity from the nucleus accumbens and marked stereotypy from the caudate-putamen whilst the primary amine, 2-amino-5,6-dihydroxy TN induced hyperactivity and stereotypy from both areas. The marked hyperactivity and stereotyped responses were inhibited by haloperidol, but not by α- or β-blockers. These data would indicate that there may be different dopamine mechanisms in the nucleus accumbens and caudate-putamen for the mediation of hyperactivity and stereotyped behaviour.