title: Changes in locomotor response to beta-endorphin microinfusion during and after opiate abstinence syndrome--a proposal for a model of the onset of mania.
abstract: Beta-Endorphin (0.3 or 0.6 nanomoles) was infused into the A10-ventral tegmental area (VTA) of male Wistar rats previously treated for 6 days with either morphine sulfate or lactose via subcutaneously implanted silastic pellets. Beta-Endorphin microinfusions occurred at 24 and 96 hours after pellets were removed. Profound changes in locomotor response to beta-endorphin were found, with morphine-pretreated rats showing a spontaneous switch from hyporesponsiveness to hyperresponsiveness over 72 hours, compared to lactose-pretreated controls. These findings may reflect on current biochemical theories regarding the "switch" process in bipolar affective disease. The data can be viewed within a heuristic model of receptor changes which may underlie the transition from depression to mania.
mesh_terms: D000341:Affective Disorders, Psychotic / Q000139:chemically induced*; D000818:Animals; D001714:Bipolar Disorder / Q000139:chemically induced*; D003913:Dextroamphetamine / Q000494:pharmacology; D004195:Disease Models, Animal; D004723:Endorphins / Q000494:pharmacology*; D006801:Humans; D008032:Limbic System / Q000187:drug effects; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology; D009434:Neural Pathways / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy*; D013681:Tegmentum Mesencephali / Q000187:drug effects; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D011954:Receptors, Dopamine; D009270:Naloxone; D001615:beta-Endorphin; D009020:Morphine; D003913:Dextroamphetamine