Central insulin inhibits hypothalamic galanin and neuropeptide Y gene expression and peptide release in intact rats.

The central actions of insulin, on galanin (GAL) and neuropeptide Y (NPY) in the brain, are examined in intact satiated rats. Ventricular injections of insulin reduce both GAL and NPY gene expression and immunoreactivity in different hypothalamic areas but have no effect in extra-hypothalamic sites. Insulin applied to medial hypothalamic fragments in vitro significantly reduces GAL and NPY release. This evidence suggests that insulin acts centrally and directly on hypothalamic peptide activity under normal feeding conditions.