Feeding effects of growth hormone-releasing factor in rats are photoperiod sensitive.
By examining the influence of photoperiod, this study extended previous findings showing that centrally administered growth hormone-releasing factor (GRF) increases feeding. Rats received intracerebroventricular injections of GRF (0, 0.4, 4.0, and 40.0 pmol) during either the light or dark phase of the photocycle. GRF produced a dose-dependent increase in 90-min food intake during the light photoperiod but a dose-dependent suppression during the dark photo-period. GRF did not significantly alter 24-hr feeding or locomotor activity, and a biologically inactive analog of GRF had no effect on feeding. Possible mechanisms underlying GRF's photoperiod dependency are discussed, including a suggestion that endogenous GRF may play a role in the regulation of circadian feeding.
Feifel
D
D
University of Toronto, Ontario, Canada.
Vaccarino
F J
FJ
D000818:Animals; D001921:Brain / Q000187:drug effects; D002940:Circadian Rhythm / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D005247:Feeding Behavior / Q000187:drug effects*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006815:Hunger / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains
D013007:Growth Hormone-Releasing Hormone