SPECIFIC-INHIBITION OF ENDOGENOUS NEUROPEPTIDE-Y SYNTHESIS IN ARCUATE NUCLEUS BY ANTISENSE OLIGONUCLEOTIDES SUPPRESSES FEEDING-BEHAVIOR AND INSULIN-SECRETION

Neuropeptide Y (NPY), which is synthesized in neurons of the arcuate nucleus (ARC) that project to different hypothalamic nuclei, is known to have potent effects on eating behavior and hormone secretion after hypothalamic administration. To test the hypothesis that endogenous NPY is essential for the normal expression of these responses, the present study used two unmodified antisense oligodeoxynucleotides (ODNs) to disrupt the synthesis of NPY in the ARC and to examine the impact of this disturbance on nutrient intake, as well as on circulating levels of insulin and the adrenal steroids, corticosterone and aldosterone. Brain-cannulated rats maintained on macronutrient diets were given daily, bilateral injections, over a 4-day period, of NPY antisense ODNs, sense ODNs or saline into the ARC. The NPY antisense ODNs produced a significant decline (- 33% relative to sense ODNs and - 40% relative to saline, P < 0.05) in NPY levels in this nucleus, without causing any direct neural damage. Peptide levels in other hypothalamic areas, namely, the paraventricular nucleus and medial preoptic nucleus, were not significantly affected. In association with this reduction in ARC NPY, the antisense-treated animals exhibited a significant decrease in feeding behavior measured during the first 90 min of the natural feeding cycle, as well as over the 24-h period. In the 90-min interval, both carbohydrate and fat intake were suppressed by 65-70% (P < 0.05, relative to both saline and sense ODNs control scores). In addition, circulating insulin levels, in blood samples taken before the initiation of feeding, were significantly reduced by 50-55% (P < 0.05 relative to both saline and sense ODNs groups), while levels of corticosterone, aldosterone or glucose were unaltered. These findings provide the first evidence for physiological disturbances that may result from an inhibition of endogenous NPY production within neurons of the ARC.