Central administration of beta-endorphin increases food intake in goldfish: pretreatment with the opioid antagonist naloxone.

The effect of intraperitoneal or intracerebroventricular beta-endorphin administration on food intake has been studied in satiated goldfish. Food intake was evaluated at different time intervals after injections, 0-2, 2-8 and 0-8 h. The 0.1 and 1 micrograms doses of beta-endorphin intracerebroventricularly administered induced an increase in food intake during the first 2 h postinjection, while no modifications on feeding were observed in the next 6 h. These same doses of beta-endorphin used increased cumulative food intake at 8 h postinjection. In contrast, intraperitoneal injection of 1 micrograms of beta-endorphin did not modify food intake in any of the studied time intervals. Naloxone, an opioid antagonist, attenuated the beta-endorphin-induced feeding increase. These results suggest that opioids may play a role in modulation of feeding central regulation, acting via opioid receptors in goldfish.