Steroids and tissue-specific modulation of galanin gene expression in the male rat reproductive system

Galanin is a neuropeptide widely distributed throughout the vertebrate neural and endocrine system. Galanin can influence pituitary hormone secretion, intestinal motility, and other biological activities. The precise physiological role of galanin is unknown. We studied the control of galanin gene expression in peripheral organs in the male rat using Northern blot and in situ hybridization techniques. In the adrenals and prostate, galanin mRNA was undetectable in the controls and did not change after the administration of dexamethasone (0.0001-10.0 mg/kg, ip) and diethylstilbestrol (0.1 mg/kg, ip). In the testis, thymus, seminal vesicles, medial basal hypothalamus, and colon, galanin message was detectable, but was not influenced by steroids. On the other hand, dexamethasone (0.5-10.0 mg/kg) was very effective in enhancing galanin expression in the vas deferens and epididymis (4- to 7-fold in the vas deferens), with a peak 6-9 h after the treatment. Diethylstilbestrol (0.1 mg/kg) stimulated galanin mRNA transcription only in the vas deferens (2- to 3-fold), with a peak 1-3 h after the treatment. Dihydrotestosterone treatment (0.2-0.4 mg/kg) was ineffective in all tissues examined. In the vas deferens and seminal vesicles, galanin mRNA has been localized at a cellular level by in situ hybridization. In these tissues only fibroblast-like cells contained the message. These data demonstrate that galanin is expressed in the male rat reproductive system and that steroid hormones participate in the control of galanin gene expression in a tissue- and hormone-specific fashion.