Food and water intake in the non-deprived pigeon after morphine or naloxone administration

Abstract

The effects of morphine and naloxone on food- and water-intake are described in the non-deprived pigeon. Morphine (1–4 mg kg −1) produced an initial suppression of both feeding and drinking, effects which could be antagonized with small doses of naloxone. A hyperdipsia occurred after treatment with certain doses of morphine, characterized by a long latency of at least 2 hr. The hyperdipsia, which was not accompanied by an increase in feeding responses, did not appear to be simply a reaction to an initial suppression of drinking. Naloxone selectively reduced food-intake, and had no effect on water-intake over the dose-range examined (0.125–8 mg kg −1). This result is in striking contrast to the results obtained in mammalian species, where drinking may be more sensitive to naloxone treatment than feeding.