Effects of Alterations in the Activity of Tuberohypophysial Dopaminergic Neurons on the Secretion of α-Melanocyte Stimulating Hormone

Abstract

Administration of γ-butyrolactone (GBL), an anesthetic which reduces dopaminergic neuronal activity, decreased the concentration of the dopamine (DA) metabolite 3,4-dihy-droxyphenylacetic acid (DOPAC) in the intermediate lobe of the pituitary gland, and increased α-melanocyte stimulating hormone (αMSH) concentrations in the serum of male rats. Bilateral electrical stimulation of the rostral arcuate nucleus, which contains perikarya of tuberohypophysial DA neurons, increased DOPAC concentrations in the intermediate lobe and decreased αMSH concentrations in the serum of GBL-anesthetized rats. Administration of the DA antagonist haloperidol prevented the decline in serum αMSH levels following arcuate nucleus stimulation, but had no effect on serum αMSH concentrations in sham-stimulated GBL-treated rats. These results indicate that GBL-induced decreases or stimulation-induced increases in the activity of tuberohypophysial DA neurons are accompanied by corresponding changes in the metabolism of DA in the intermediate lobe of the rat pituitary gland, and by reciprocal changes in the secretion of αMSH.