title: Changes in morphine self-administration after exposure to ionizing radiation: evidence for the involvement of endorphins.
abstract: Recent findings have implicated endogenous opiates in radiation-induced behavioral change. The present experiment further investigated this hypothesis by observing alterations in morphine self-administration after irradiation. Under the presumption that the release of endogenous opiates would decrease the need for exogenously supplied morphine, we hypothesized that after radiation exposure morphine-experienced mice would self-administer less of the opiate. C57BL/6J mice had continuous access to two drinking flasks which contained either water or morphine in saccharine water. Irradiated mice drank significantly less morphine than did sham-irradiated controls. This decrease was naloxone-reversible and could not be entirely attributed to a generalized radiogenic hypodipsia or taste aversion. These results are consistent with the hypothesis that radiation-induced behavioral changes may be due, in part, to the fluctuations of endogenous opiates.
mesh_terms: D000818:Animals; D003037:Cobalt Radioisotopes; D004327:Drinking Behavior / Q000187:drug effects / Q000528:radiation effects*; D004723:Endorphins / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000008:administration & dosage*; D009270:Naloxone / Q000494:pharmacology*; D012439:Saccharin; D012996:Solutions
chemical_list: D003037:Cobalt Radioisotopes; D004723:Endorphins; D012996:Solutions; D009270:Naloxone; D009020:Morphine; D012439:Saccharin