EFFECT OF ISOLATION ON PAIN THRESHOLD AND ON DIFFERENT EFFECTS OF MORPHINE

1. The effect of three periods of isolation (8, 15 and 30 days) were s tudied in mice on the pain treshold and the sensitivity to morphine. 2 . The pain threshold was unchanged after 8 and 15 days of isolation bu t increased after 30 days of isolation. 3. The analgesic effect of mor phine was unchanged after 8 and 15 days of isolation but increased aft er 30 days of isolation. 4. The tolerance to morphine analgesia was un changed after 8 and 15 days of isolation but increased after 30 days o f isolation (morphine-induced analgesia was reduced). 5. The physical dependence on morphine induced by precipitated withdrawal was unchange d after 8 and 15 days of isolation but decreased after 30 days of isol ation. 6. It is suggested that isolation may modify the metabolism the metabolism/absorption of morphine in a different way according as the treatment is unique or chronic. (C) 1997 Elsevier Science Inc.