EFFECT OF MORPHINE AND ABSTINENCE SYNDROME ON [H-3] BROMOXIDINE BINDING TO ALPHA(2)-ADRENOCEPTORS IN RAT-BRAIN

At 4 days after the implantation of two subcutaneous 75 mg morphine pe llets in the back skin, rats were morphine-dependent. In the three lay ers studied in the occipital cortex we found that the values of the al pha(2)-adrenergic agonist [H-3]bromoxidine binding increased with resp ect to animals implanted with placebo pellets. Typical behavioral and physiological symptoms of the abstinence syndrome appeared 30 minutes after administration of naloxone, [H-3]bromoxidine binding values bein g similar to those obtained in animals implanted with placebo pellets. The pattern of response of the [H-3]bromoxidine binding was similar i n the hippocampus and the superficial gray layer of the superior colli culus of the mesencephalon, but the differences were not statistically significant in these areas. This paper concludes that exist brain reg ional differences in the alpha(2)-adrenoceptors response under morphin e-treatment and possibly under naloxone-induced morphine abstinence sy ndrome.