Narcotic analgesics and stereotyped behaviour in mice

In this paper we have studied the effects of morphine, codeine, fentanyl, pentazocine, etorphine and fluphenazine (all drugs injected i.p.) on stereotyped behaviour induced by methylphenidate 60 mg/kg i.p., as well as induced by apomorphine 5 mg/kg s.c. in mice. It was found that all used analgesics and fluphenazine dose--dependently inhibited the intensity of methylphenidate--induced gnawing in mice. This effect of analgesics, but not that of fluphenazine was antagonized by naloxone (0.8 mg/kg i.p.) and nalorphine (10 mg/kg i.p.). Climbing behaviour induced by apomorphine was not reduced by narcotic analgesics, but fluphenazine inhibited this effect dose--dependently. These findings give the behavioural support that analgesics applied have antidopaminergic activity in mice.