The action of chlorpromazine upon the serum and hypophyseal variations of growth hormone, prolactin and TSH in the male adult rat under continuous-lighting stress.

The influence of chlorpromazine (CPZ) on the serum and hypophyseal levels of growth hormone (GH), prolactin and TSH was studied in the male adult rat occurring under normal light-dark-rhythm conditions and under continuous 24-hour lighting, respectively. The serum and hypophyseal concentrations of GH decreased significantly (p less than 0.01 and p less than or equal to 0.02) one hour after the administration of 1.0 mg of CPZ in the animals under continuous light by comparison with the animals maintained on the same conditions. In the animals under normal light-dark rhythm, CPZ did not influence the peripheral or central concentrations of GH. The animals maintained either in normal or in continuous lighting conditions released prolactin under the influence of CPZ. The increased values of circulating TSH in light-exposed animals by comparison with the diurnal group (p less than 0.001) were some more augmented under the influence of CPZ, while this drug remained unefficient in the animals under normal light-dark-rhythm conditions. The mechanism of CPZ action upon the secretion of GH and prolactin, which are hormones lacking target gland, is discussed.