Differences in morphine reinforcement property in two inbred rat strains: associations with cortical receptors,behavioral activity,analgesia and the cataleptic effects of morphine |
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Authors: | Sergey K. Sudakov Steven R. Goldberg Elena V. Borisova Lidia A. Surkova Irina V. Turina Dimitrij Ju. Rusakov Gregory I. Elmer |
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Affiliation: | (1) Laboratory of Experimental Therapy of Drug Abuse, Institute of Medico-Biological Problems of Addiction, All-Union Research Center of Addictions, Malyi Mogiltzevskij per.3, 121002 Moscow, Russia;(2) Behavioral Pharmacology and Genetics Section, Preclinical Pharmacology Laboratory, National Institute on Drug Abuse, Addiction Research Center, Box 5180, 21224 Baltimore, Maryland, USA |
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Abstract: | The purpose of the current study was to investigate genetic differences between two inbred strains of rats, Fisher-344 (F344/N) and Wistar Albino Glaxo (WAG/GSto), in a number of drug-naive and drug-related behaviors, including oral and intravenous morphine self-administration. F344/N and WAG/GSto rats differed in drug-naive behaviors such as nociception, rearing and sensitivity to lick suppression tests but did not differ in locomotor activity, ambulation or grooming behavior. F344/N rats were less sensitive to thermal stimuli as measured via tail-flick response, and more sensitive to the suppressive effects of intermittent shock in a lick suppression test. The F344/N rats demonstrated a significantly greater amount of rearing in open field tests but did not differ from WAG/GSto rats in locomotor activity, ambulation or grooming behavior. In addition to the behavioral results, naive F344/N and WAG/GSto rats were found to differ in and 2 receptor concentrations (F344/N>WAG/GSto) and in 5HT2 and D2 affinity constants (WAG/GSto>F344/N). These two inbred rat strains also differed in drug-related behaviors. F344/N rats showed significantly greater depression of locomotor activity at morphine 3 mg/kg than WAG/GSto rats. In addition, F344/N rats consumed significantly greater amounts of morphine in a two-bottle choice procedure and morphine maintained significantly greater amounts of behavior during intravenous self-administration sessions. Importantly, drug maintained behavior was significantly greater than with vehicle only in the F344/N rats during operant self-administration sessions. |
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Keywords: | Morphine Behavioral activity Analgesia Rat Self-administration Genetics |
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