Fos-like immunoreactivity in the brainstem of the rat following peripheral administration of cholecystokinin.

Ninety min after intraperitoneal (ip) injection of Cholecystokinin (CCK, 50 μg/kg body wt) Fos-like protein was expressed in cells throughout the nucleus of the tractus solitarii (NTS) and area postrema, and also in scattered cells in the lateral reticular area of the brainstem. Using dual fluorescent immunocytochemistry for Fos-like protein and tyrosine hydroxylase (TH), catecholaminergic cells in the A2 region of the NTS and the A1 region of the lateral reticular area were shown to be activated.