Sulpride inhibits the effects of ghrelin on thyroid hormones secretions in rats

Because of physiological importance of ghrelin, in the present study, the role of dopaminergic D2 receptor was determined on mediating the inhibitory effects of ghrelin on thyroid hormones secretions. Twenty rats weighing 200-230g in four groups received saline, ghrelin, ghrelin plus sulpride(via third cerebral ventricle or intraperitoneally). Blood samples were collected thirty minutes following injections. Mean serum triiodothyronine (T3) and thyroxine (T4) concentrations were measured by using T3 and T4 kits and the method of radio- immunoassay (RIA). Ghrelin significantly decreased mean serum thyroid hormones level. While both centrally or peripherally injections of sulpride increased the mean serum T3 or T4 levels compared to ghrelin. D2 dopaminergic receptor subtype may be involved in mediating the influences of ghrelin actions on hypothalamic- pituitary- thyroid axis.