Distribution and regulation of galanin-like peptide (GALP) in the hypothalamus of the mouse

Galanin-like peptide (GALP) is a newly discovered molecule whose expression in the brain is confined to the arcuate nucleus and median eminence. In th e rat, cellular levels of GALP mRNA are reduced by fasting and reversed by peripheral administration of leptin. The purpose of this investigation was 1) to clone and map the distribution of GALP mRNA in the brain of the mouse ; 2) to compare the pattern and magnitude of GALP mRNA expression in the le ptin-deficient obese (ob/ob) mouse with that of wild-type controls; and 3) to examine the effects of leptin delivered into the brain on the expression of GALP mRNA in the ob/ob mouse. We report the sequence of a mouse GALP cD NA and show that GALP mRNA is expressed in the arcuate nucleus, median emin ence, infundibular stalk, and the neurohypophysis of this species. The expr ession of GALP mRNA in the brain was markedly reduced in the ob/ob mice, co mpared with wild-type animals. Intracerebroventricular infusion of leptin t o ob/ob mice increased both the number of GALP mRNA-expressing neurons and their content of GALP mRNA compared with vehicle-treated controls. These ob servations demonstrate that GALP mRNA is induced by leptin through a direct action on the brain.