Abstract
We have examined the effects of sulpiride on locomotor activity, food intake and body temperature in mice dependent to morphine by twice daily i.p. injections for 3 days of morphine hydrochloride (40 mg/kg). Administered in a single 10 mg/kg dose, sulpiride reduced locomotor activity and increased food intake in normal but not in morphine-dependent mice. Also, sulpiride at a higher dose of 80 mg/kg was hyperthermic in normal mice but did not change the body temperature of morphine-dependent mice. We suggest that the attenuation of the effects of sulpiride in morphine-dependent mice was due to dopamine receptor supersensitivity. LD50 determination, on the other hand, indicated increased toxicity of sulpiride in morphine-dependent mice in comparison with matched controls not treated with morphine. (C) 1998 Chapman & Hall Ltd.