Nitrous oxide induces feeding in the nondeprived rat that is antagonized by naltrexone.
Three experiments investigated a possible effect of nitrous oxide (N2O) on food intake in nondeprived male hooded rats in independent groups designs. Experiment 1 demonstrated a concentration-related increase in intake with increasing level of nitrous oxide (10-40% N2O), reaching statistical significance at 20% N2O when compared to room air controls (p < 0.05). In experiment 2, pretreatment with 10 and 20 mg/kg of the benzodiazepine antagonist, flumazenil, failed to significantly attenuate 30% N2O-induced hyperphagia. In Experiment 3, pretreatment with the opioid antagonist, naltrexone, effectively antagonized 30% N2O-induced hyperphagia. Pronounced attenuation (to 59% of 30% N2O-induced intake level over a 1 h period) at the lowest dose of naltrexone (0.1 mg/kg, p < 0.01) compared to vehicle level resulted in a shallow dose-response curve across the dose range tested (0.1-10.0 mg/kg). These results suggest that an endogenous opioid mechanism is prominently involved in the N2O-induced ingestive response.
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Department of Psychology, Marquette University, Milwaukee, WI 53233, USA.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D005247:Feeding Behavior / Q000187:drug effects*; D005442:Flumazenil / Q000494:pharmacology; D018757:GABA Modulators / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D008297:Male; D009271:Naltrexone / Q000494:pharmacology*; D009609:Nitrous Oxide / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats
D018757:GABA Modulators; D058787:GABA-A Receptor Antagonists; D005442:Flumazenil; D009271:Naltrexone; D009609:Nitrous Oxide