Effects of opiate antagonists and of morphine on chlordiazepoxide-induced hyperdipsia in the water-deprived rat.
The effects of naloxone hydrochloride (0.01-10 mg X kg-1), naltrexone hydrochloride (0.01-10 mg X kg-1), and morphine sulphate (0.01-10 mg X kg-1) on the increased water consumption provoked by administration of chlordiazepoxide (10 mg X kg-1) were investigated in male rats which had been adapted to a 22 hr water-deprivation schedule. As previously reported, both naloxone and naltrexone dose-relatedly reduced water ingestion. Naloxone at 1 mg X kg-1 and naltrexone at 0.1 mg X kg-1 completely blocked the chlordiazepoxide-induced hyperdipsia. Since both opiate antagonists removed the chlordiazepoxide-induced effects in small doses, their effect can plausibly be attributed to opiate receptor blockade. Hence, chlordiazepoxide-induced hyperdipsia may depend upon the activation of endogenous opioid mechanisms. Morphine had little effect on drinking, unless a large dose (10 mg X kg-1) was used, when the thirst-induced and chlordiazepoxide-induced drinking were attenuated. The data provided no evidence that morphine, a mu opiate agonist, enhanced chlordiazepoxide-induced water consumption. The results are considered in relation to other relevant behavioural and biochemical findings.
D000704:Analysis of Variance; D000818:Animals; D002707:Chlordiazepoxide / Q000494:pharmacology*; D004326:Drinking / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D051381:Rats; D013894:Thirst / Q000187:drug effects*; D014868:Water Deprivation
D009292:Narcotic Antagonists; D009270:Naloxone; D009271:Naltrexone; D002707:Chlordiazepoxide; D009020:Morphine