INTRAVENTRICULAR-INJECTION OF NEUROPEPTIDE-Y ANTISERA CURBS WEIGHT-GAIN AND FEEDING, AND INCREASES THE DISPLAY OF SEXUAL BEHAVIORS IN OBESEZUCKER FEMALE RATS

Obese Zucker rats are hyperphagic, overweight, and infertile. It has b een postulated that neuropeptide Y (NPY) overproduction may contribute to obesity and infertility in these animals. To test this hypothesis, ovariectomized, adult obese Zucker rats were implanted with cannulae in the third ventricle and subsequently injected with NPY antisera or normal rabbit sera (NRS) 6, 4 and 2 h before experimental observation. Steroid-treated females injected with NPY antisera were significantly more receptive and were more likely to show preceptive behaviors than after treatment with NRS (e.g., lordosis quotient: NPY antisera, 65.5 +/-6.9%; NRS, 30.9+/-11.6%, P < 0.02; 91% displaying proceptivity afte r NPY antisera injection vs. 36% after NRS, P < 0.03). Injection of NP Y antisera also curbed food intake and weight gain (24 h food intake: NPY antisera, 10.5+/-2.1 g; NRS, 20.5+/-1.7 g, P < 0.01; 24 h weight g ain: NPY antisera, - 5.4+/-2.2 g; NRS, 5.8+/-0.7 g, P < 0.01). Locomot or activity was similar after NRS and NPY antisera treatment (P > 0.5) suggesting that general malaise was not responsible for the effects o f NPY antisera on food intake or body weight. These data suggest that endogenous neuropeptide Y contributes to excessive feeding and weight gain, and suppressed reproductive behaviors in obese Zucker female rat s. (C) 1998 Elsevier Science B.V. All rights reserved.