Galanin in adrenocorticotropic hormone cells is decreased by castration

Abstract

Galanin (GAL) is a neuropeptide that is widely expressed in neuroendocrine tissues, including the adenohypophysis. Since GAL is expressed at higher levels in females, little attention has been paid to the regulation of GAL secretion in males. Here, we show that testosterone regulates GAL secretion in the adenohypophysis of male rats. Using double immunoelectron microscopy, we demonstrate that GAL cells possess three types of secretory granule: those with colocalization of GAL and adrenocorticotropic hormone (ACTH), those with GAL only, and those with ACTH only. The predominant granule type was that containing both GAL and ACTH, suggesting that GAL and ACTH are secreted at the same time. Indeed, adrenalectomy induced an acute decrease in the number of both GAL cells and ACTH cells. In contrast, castration resulted in a decrease in the proportion of GAL cells, while the proportion of ACTH cells remained unchanged. In addition, ACTH-strongly positive and GAL-positive cells were decreased while ACTH-weakly positive and GAL-negative cells were increased after castration. Testosterone treatment of castrated animals resulted in restoration of these levels to those of intact and sham operated animals. These results indicated that testosterone regulates GAL secretion in male animals.

The regulative effect of galanin family members on link of energy metabolism and reproduction

“…An operation of castration in the adult male rats resulted in a significant decrease in the number of cells which expressed galanin mRNA and the average grains per cell in the adenohypophysis, which may be reversed by the replenishment with testosterone to the levels of intact or sham operated animals[23, 121,155]. The divergent effects of testosterone on galanin expression, perhaps, resulted from different tissues and species observed.Interestingly, the fluctuations in a photoperiod-driven seasonal rhythm may affect the secretion of sex steroids, resulting in a corresponding change of galanin expression in neurons of the bed nucleus of the hamsters[20].…”

Single‐nucleotide polymorphism rs948854 in human galanin gene and multiple sclerosis: a gender‐specific risk factor

“…Given the established role of galanin in the production of luteinizing hormone (LH; Lopez, Negro‐Vilar, ; Scheffen et al, ), which in turn regulates production of testosterone, the proposed changes in galanin production resulting from polymorphism in the GAL promoter is likely to affect the functioning of HPGA in males. Furthermore, the stimulatory effect of testosterone on galanin production (Bouret et al, ; Sato and Yamaguchi, ) suggests positive feedback mechanisms that might be essential for the proposed compensatory effect of testosterone in younger males among our cohort. Although it remains to be determined whether A‐to‐G substitution in rs948854 reduces GAL transcription, a subsequent reduction in the galanin level, if confirmed, likely contributes to the increased susceptibility to MS, whereas testosterone may temporarily protect male carriers from MS onset.…”