Opiates and the anorexia of uremia.

Uremia results in a decrease in food intake. In the present study we investigated whether opiates known to stimulate feeding would alter food intake in rats made uremic by 1 and 5/6 nephrectomy. Morphine increased food intake in sham nephrectomized rats, but failed to alter food intake in uremic animals and depressed the ingestion of rat chow in a group of weight restricted rats. Butorphanol tartrate increased feeding in sham and uremic animals but did not alter intake in the weight restricted group. Higher doses of butorphanol were needed to stimulate feeding in the uremic rats compared to the sham group, suggesting a relative resistance to opioid-induced feeding in the uremic rats. The opiate antagonist, naloxone, suppressed food intake in the uremic and sham groups more effectively than in the weight restricted rats. These data suggest that the opioid feeding system functions in a reduced fashion in uremic rats, but probably is not the sole factor involved in producing the anorexia associated with uremia.