| Abstract: | Rats subjected to prolonged restraint showed an increase in tail flick latency which outlasted the period of restraint by 15 min. This restraint could be blocked but not reversed by 1 mg/kg of naltrexone hydrochloride given subcutaneously. Naltrexone methobromide, administered subcutaneously in doses of 10 or 25 mg/kg, did not block the analgesia indicating that peripheral opioid receptors were probably not involved. Naltrexone hydrochloride was shown to have no effect on brain tryptophan uptake in restrained rats, a neurochemical event which had previously been shown to be critical to restraint-induced analgesia. |
