Peripheral administration of butorphanol tartrate markedly enhanced feeding from 0800 to 1400 hours when compared with vehicle controls. Butorphanol tartrate feeding was not antagonized by doses of naloxone as high as 10 mg/kg. These data support the concept that the kappa or sigma opiate receptors are involved in feeding behavior. It is well recognized that the endogenous opiates play a role in the central regulation of appetite (1, 2, 3, 4). Numerous studies have shown that The endogenous opioid peptides and morphine can initiate feeding under various conditions (5-12) whereas the opiate antagonist, naloxine can reduce food consumption (13-20). Recently, the endogenous opiod peptide, dynorphin, has been reported to enhance food intake (12-25). Much evidence has been accumulated indicating that a number of opiate receptors are present in the brain, each one having a high affinity for a specific endogenous opioid peptide (26, 27). Both the cyclazocine related compounds (28) and the feeding enhancer, dynorphin (29-32), have been reported to be specific kappa receptor agonists. In the present study, we report on the effect of the morphinan congener, butorphanol tartrate (33), on ingestive behaviour.
Bibliographical noteFunding Information:
We thank JoAnn Tallman for her expert secretarial aid and Martha Grace and Julie Kneip for their excellent technical assistance. We also thank Mohammad Khosti of Bristol Laboratories and Endo Laboratories for kindly supplying drugs for this study. This research was supported by the Veterans Administration.