Galanin injection into the nucleus of the solitary tract stimulates feeding in rats with lesions of the paraventricular nucleus of the hypothalamus.

Feeding can be stimulated by injection of galanin into the area postrema/nucleus of the solitary tract (AP/NTS) or fourth ventricle (4V). However, the threshold for galanin-induced feeding is lower when galanin is injected into the paraventricular nucleus of the hypothalamus (PVN) than when injected into the NTS. The greater apparent sensitivity of the PVN to galanin and the proximity of this nucleus to the third ventricle raise the possibility that galanin injected into the AP/NTS or 4V may stimulate feeding by accessing receptors in the PVN rather than by a local action in the hindbrain. To assess this possibility, feeding in response to NTS galanin was evaluated in rats with bilateral electrolytic lesions of the PVN. We found that PVN lesions did not abolish feeding induced by injections of galanin into the NTS. Rather, galanin-induced feeding, but not mercaptoacetate- or 2-deoxy-D-glucose-induced feeding, was significantly enhanced in PVN-lesioned rats compared to sham-operated controls. These results suggest that galanin receptors in the NTS region mediate feeding in response to galanin and that the galaninergic nerve terminals innervating these receptors may originate in part from cell bodies in the PVN.