Socially induced morphine pseudosensitization in adolescent mice.
Given that social influences are among the strongest predictors of adolescents' drug use, this study examined the effect of social interaction on morphine-induced hyperlocomotion in both adolescent and adult mice. Three experimental groups of adolescent and adult male mice were examined (i) morphine-treated mice (twice daily, 10-40 mg/kg, subcutaneous), (ii) saline-injected mice housed together with the morphine-treated mice ('saline cage-mates'), and (iii) saline-injected mice housed physically and visually separated from the morphine-treated mice ('saline alone'). After the treatment period, mice were tested individually for their locomotor response to 10 mg/kg morphine (subcutaneous). Adolescent saline cage-mates, though administered morphine for the very first time, exhibited an enhanced hyperlocomotion response similar to the locomotor sensitization response exhibited by the morphine-treated mice. This was not observed in adults. In adults, there were no significant differences in morphine-induced hyperlocomotion between saline alone and saline cage-mates. As expected, morphine-treated adults and adolescents both exhibited locomotor sensitization. These results show a vulnerability to social influences in adolescent mice, which does not exist in adult mice.
Hodgson
Stephen R
SR
Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, Texas 77843, USA.
Hofford
Rebecca S
RS
Roberts
Kris W
KW
Wellman
Paul J
PJ
Eitan
Shoshana
S
D000375:Aging / Q000187:drug effects*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D007398:Interpersonal Relations; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D009294:Narcotics / Q000494:pharmacology*
D009294:Narcotics; D009020:Morphine