LIKE GALANIN, THE 60-amino acid peptide, galanin-like peptide (GALP), has orexigenic actions, demonstrated by an acute increase in feeding after central injection in rodents. However, in contrast to galanin, GALP causes a prolonged rise in core body temperature and a reduction in body weight over 24 h. In an attempt to identify potential explanations for the observed differences between GALP and galanin this study examined which brain areas were activated by these peptides.

Intracerebroventricular (icv) injection of GALP into conscious rats significantly stimulated feeding over 0-1 h, increased core body temperature, but reduced body weight gain over 24 h. Immunohistochemistry to detect c-Fos demonstrated that icv injection of GALP or galanin activated several brain regions in common, including the dorsomedial nucleus of the hypothalamus, the lateral hypothalamus, and the nucleus tractus solitarius (NTS) of the brain stem. However, GALP also induced c-Fos expression in the periventricular hypothalamic region and supraoptic hypothalamic nucleus (SON).

Cell activation induced by GALP in the SON and the NTS was dependent on food intake, but was independent of food consumption in all other brain regions. Double immunohistochemistry indicated that small cells expressing c-Fos in the periventricular hypothalamic region after GALP were astrocytes and not microglia.