Galanin coexists with vasopressin in the normal rat hypothalamus and galanin's synthesis is increased in the Brattleboro (diabetes insipidus) rat.

Galanin is a peptide containing 29 amino acid residues, that is present in the median eminence, in the magnocellular neurons of the supraoptic (SON) and paraventricular nuclei (PVN) of the rat hypothalamus and in the posterior pituitary. We report here that: (1) immunoreactivity for galanin (GAL) and vasopressin coexist in the SON of normal rats, (2) levels of mRNA encoding preprogalanin are markedly elevated in the PVN and SON of Brattleboro (diabetes insipidus) rats, as determined by in situ hybridization histochemistry but (3) levels of GAL-like immunoreactivity (GAL-LI) are significantly reduced in the posterior pituitary of these rats, as determined by radioimmunoassay. We suggest that production and possibly secretion of the peptide GAL may be increased in the Brattleboro rat.