title: Irradiation exposure modulates central opioid functions.
abstract: Exposure to low doses of gamma irradiation results in the modification of both the antinociceptive properties of morphine and the severity of naloxone-precipitated withdrawal in morphine-dependent rats. To better define the interactions between gamma irradiation and these opiate-mediated phenomena, dose-response studies were undertaken of the effect of irradiation on morphine-induced antinociception, and on the naloxone-precipitated withdrawal syndrome of morphine-dependent rats. In addition, electrophysiologic studies were conducted in rats after irradiation exposure and morphine treatment correlating with the behavioral studies. The observations obtained demonstrated that the antinociceptive effects of morphine as well as naloxone-precipitated withdrawal were modified in a dose-dependent manner by irradiation exposure. In addition, irradiation-induced changes in the evoked responses obtained from four different brain regions demonstrated transient alterations in both baseline and morphine-treated responses that may reflect the alterations observed in the behavioral paradigms. These results suggest that the effects of irradiation on opiate activities resulted from physiologic alterations of central endogenous opioid systems due to alterations manifested within peripheral targets.
authors: Department of Neurobiology and Anatomy, University of Texas Medical School, Houston 77025.
authors: P M
authors: PM
authors: Dougherty
authors: N
authors: N
authors: Dafny
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000528:radiation effects; D001921:Brain / Q000502:physiology* / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D008297:Male; D009020:Morphine / Q000009:adverse effects / Q000494:pharmacology*; D009270:Naloxone; D009619:Nociceptors / Q000528:radiation effects*; D051381:Rats; D011916:Rats, Inbred F344; D011919:Rats, Inbred Strains; D013375:Substance Withdrawal Syndrome / Q000139:chemically induced / Q000503:physiopathology
chemical_list: D009270:Naloxone; D009020:Morphine