Hypophysis -Epiphyseal Interactions: Effects of Corticotropin on Metabolism of Serotonin and Formation of a Melatonin Night-Time Peak

In experiments on Wistar mature male rats, we studied the effects of injections of corticotropin (ACTH; single or five daily introductions, 1 U per day) on metabolism of epiphyseal serotonin. Injections of ACTH intensified the process of formation of a night-time peak of melatonin synthesis in the epiphysis at the expense of enhancement of utilization of tryptophan by pinealocytes and its subsequent transformation into serotonin, as well as of intensification of reactions of N-acetylation and subsequent O-methylation of the latter. The observed changes are considered an analog of the defense reaction of the organism to the negative action of an excess of hormones of the hypophyseal-adrenocortical axis in stress.