ABSTRACT
The effects of dopamine on the release of thyrotropin-releasing hormone (TRH) from the rat retina in vitro were studied. The rat retina was incubated in the medium 199 (pH 7.4) with 1.0 mg/ml of bacitracin and 100 micrograms/ml of ascorbic acid. The amount of TRH release into the medium was measured by radioimmunoassay. The TRH release from the rat retina was inhibited significantly in a dose-related manner with the addition of dopamine, but not with pimozide. The inhibitory effects of dopamine on TRH release from the rat retina were blocked with an addition of pimozide to the medium. The elution profile of methanol-extracted rat retina on sephadex G-10 was identical to that of synthetic TRH. From these findings it is concluded that the dopaminergic system inhibits TRH release from the rat retina in vitro.
Subject(s)
Dopamine/pharmacology , Retina/drug effects , Thyrotropin-Releasing Hormone/metabolism , Analysis of Variance , Animals , Dopamine Antagonists , Dose-Response Relationship, Drug , In Vitro Techniques , Male , Pimozide/pharmacology , Radioimmunoassay , Rats , Rats, Inbred Strains , Retina/metabolismABSTRACT
Effects of acetylcholine on the release of thyrotropin-releasing hormone (TRH) from the rat retina were studied in vitro. The retina was incubated in medium 199 (pH 7.4) with 1.0 mg/ml of bacitracin and 100 micrograms/ml of ascorbic acid (medium) for 20 min. The amount of TRH release into the medium was measured by radioimmunoassay. The TRH release from the rat retina was enhanced significantly in a dose-related manner with the addition of acetylcholine and inhibited with addition of atropine. The stimulatory effect of acetylcholine on TRH release from the retina was blocked with the addition of atropine. The elution profile of methanol-extract of the rat retina was identical to that of synthetic TRH. The findings suggest that the cholinergic system stimulates TRH release from the rat stomach in vitro.