THE ROLE OF DOPAMINE-RECEPTORS IN THE RELEASE OF THYROTROPIN-RELEASING-HORMONE FROM THE RAT STRIATUM AND NUCLEUS-ACCUMBENS - AN IN-VITRO STUDY

In the present study we examined the influence of dopamine (DA) stimul ants: amphetamine (an agent releasing DA), apomorphine (a non-selectiv e agonist of DA receptors), quinpirole (a selective agonist of D2 rece ptors) and SKF-38393 (a selective agonist of D1 receptors) on the in v itro release of thyrotropin-releasing hormone (TRH) from the rat stria tal slices and nucleus accumbens fragments. It was shown that amphetam ine, apomorphine and quinpirole (all those drugs added in concentratio ns of 10(-8)-10(-5)M), concentration-dependently increased the release of TRH, a more potent effect being observed in striatal slices. On th e other hand, SKF-38393 (10(-6)-10(-5)M) was ineffective. Furthermore, the increases in the TRH release from the striatal slices, induced by 10(-5)M of amphetamine, apomorphine or quinpirole, were completely bl ocked by the selective D2 receptor antagonist sulpiride (10(-5)M), but not by the selective D1 receptors antagonist SCH-23390 (10(-5)M). The se results indicate that stimulation of D2 receptors is responsible fo r the TRH release from the striatum and nucleus accumbens in vitro, an d that this effect may be involved in the decrease in the peptide cont ent in the striatum following DA stimulants, observed earlier in in vi vo studies.