Naloxone reduces the feeding evoked by intracerebroventricular galanin injection.
Central injection of galanin elicits feeding in satiated rats. We recently observed galanin-immunoreactive fibers in synaptic connection with a population of beta-endorphin-immunopositive cell bodies and dendrites in the basal hypothalamus. Because beta-endorphin also stimulates food intake, these morphological findings raised the possibility that stimulation of feeding by galanin may, in part, be mediated by beta-endorphin release. First, we observed that ICV injection of galanin (1.5-6.0 nmol) stimulated feeding in a dose-related fashion. Next, the effect on food intake of the opioid receptor antagonist naloxone (20-200 micrograms, ICV) administered immediately preceding galanin (3 nmol, ICV) was evaluated. Galanin-induced feeding was suppressed by naloxone in a dose-dependent manner with a maximal suppression of 76% at the highest naloxone dose. These findings support the existence of a functional link between galanin and beta-endorphin and are in accord with the view that stimulation of food intake by galanin may, in part, be mediated by increased beta-endorphin release.
Dube
M G
MG
Department of Physiology, University of Florida College of Medicine, Gainesville 32610.
Horvath
T L
TL
Leranth
C
C
Kalra
P S
PS
Kalra
S P
SP
D000818:Animals; D001921:Brain / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects*; D019004:Galanin; D007031:Hypothalamus / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009479:Neuropeptides / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D010455:Peptides / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000187:drug effects; D012527:Satiation / Q000187:drug effects
D009479:Neuropeptides; D010455:Peptides; D011957:Receptors, Opioid; D009270:Naloxone; D019004:Galanin