AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 3 701-R706, Copyright © 1989 by American Physiological Society
Prolactin stimulates food intake in the absence of ovarian progesterone
T. Gerardo-Gettens, B. J. Moore, J. S. Stern and B. A. Horwitz
Department of Animal Physiology and Nutrition, University of California, Davis 95616.
Increases in serum estrogen inhibit food intake. Conversely, progesterone
stimulates food intake, probably via its antiestrogenic action. We have
reported that elevated serum prolactin also stimulates food intake in
female rats. It is unclear whether this effect is mediated through elevated
levels of progesterone. The present study investigated the effects of
prolactin on food intake and brown fat activity in the absence of
progesterone. Female Osborne-Mendel rats were assigned to one of six
groups: sham operated (Sham, n = 10), ovariectomized (OVX, n = 10), OVX +
low estrogen (EL, n = 11), OVX + EL + prolactin (PIT, n = 9), OVX + high
estrogen (EH, n = 10), and OVX + EH + PIT (n = 8). Estrogen levels were
elevated by Silastic implants. Prolactin levels were elevated through
pituitary transplants placed under the kidney capsule. Nine days
postsurgery, food intake was significantly higher in OVX vs. Sham rats.
Estrogen-treated rats (OVX + EL and OVX + EH) had significantly suppressed
food intake values compared with both Sham and OVX animals. Finally,
hyperprolactinemic rats (OVX + EL + PIT and OVX + EH + PIT) ate
significantly more food than did estrogen-treated rats without pituitary
explants. Despite the hyperphagia, no significant differences in brown fat
GDP binding were observed. These data indicate that prolactin stimulates
food intake in the absence of ovarian progesterone.
