The role of dopamine in regulation of thyrotropin-releasing hormone in the striatum and nucleus accumbens of the rat

Abstract

The effect of α-methyl-p-tyrosine (α-MT), FLA-63, amphetamine, apomorphine and quinpirole on the concentration of thyrotropin-releasing hormone (TRH) in the striatum and nucleus accumbens was studied in rats. It has been found that the TRH content was increased in both those structures after α-MT, an inhibitor of tyrosine hydroxylase which reduced the concentration of both dopamine (DA) and noradrenaline (NA), but not after FLA-63, an inhibitor of DA-β-hydroxylase which decreased the NA level without affecting DA. On the other hand, the indirectly acting dopaminomimetic amphetamine, the non-selective DA receptor agonist apomorphine, and the selective D 2 receptor agonist quinpirole reduced the TRH level in the striatum, but not in the nucleus accumbens. Moreover, the decrease in the striatal peptide content induced by DA-mimetics was antagonized by the selective D 2-receptor antagonist sulpiride, but not by the selective D 1 receptor antagonist SCH 23390. The effect of amphetamine was not modified by the selective α 1-adrenoceptor antagonist prazosin. These results indicate that DA and D 2 receptors play a significant rleo in the regulation of the striatal TRH.