[Effects of dietary proteins on analgesic activity of tolerance and physical dependence on morphine in rats].

Effects of dietary proteins such as casein and egg albumin on analgesic activity of, tolerance to and physical dependence on morphine in rats were examined. There was no difference in analgesic activity after acute administration of morphine 10 mg/kg, s.c. between rats treated with casein food or egg albumin food and normal food for 5 or 21 days. The development of tolerance to morphine analgesia in rats treated with albumin food but not with casein food was suppressed during daily morphine 10 mg/kg, s.c. on 5 consecutive days. Rats were treated with casein or albumin food mixed with morphine (0.5 mg/g of food) for 5 days. Morphine intake in rats treated with albumin food was significantly decreased as compared to that with morphine admixed casein or normal food. Body weight loss by naloxone in morphine-dependent rats was significantly less in both casein food and albumin food groups than in the normal food group. These results suggest that chronic dietary treatment with albumin may produce a partial inhibition of development of tolerance to morphine analgesia and that with casein may attenuate morphine withdrawal manifestation in rats.