title: Social influences on morphine-conditioned place preference in adolescent BALB/cJ and C57BL/6J mice.
abstract: BACKGROUND
  Among human adolescents, drug use is substantially influenced by the attitudes and behaviors of peers. Social factors also affect the drug-seeking behaviors of laboratory animals. Conditioned place preference (CPP) experiments indicate that social context can influence the degree to which rodents derive a rewarding experience from drugs of abuse. However, the precise manner by which social factors alter drug reward in adolescent rodents remains unknown.
  
  
  OBJECTIVE
  We employed the relatively asocial BALB/cJ (BALB) mouse strain and the more prosocial C57BL/6J (B6) strain to explore whether "low" or "high" motivation to be with peers influences the effects of social context on morphine CPP (MCPP).
  
  
  METHODS
  Adolescent mice were conditioned by subcutaneous injections of morphine sulfate (0.25, 1.0, or 5.0 mg/kg). During the MCPP procedure, mice were housed in either isolation (Ih) or within a social group (Sh). Similarly, following injection, mice were conditioned either alone (Ic) or within a social group (Sc).
  
  
  RESULTS
  Adolescent B6 mice expressed a robust MCPP response except when subjected to Ih-Sc, which indicates that, following isolation, mice with high levels of social motivation are less susceptible to the rewarding properties of morphine when they are conditioned in a social group. By contrast, MCPP responses of BALB mice were most sensitive to morphine conditioning when subjects experienced a change in their social environment between housing and conditioning (Ih-Sc or Sh-Ic).
  
  
  CONCLUSIONS
  Our findings demonstrate that susceptibility to morphine-induced reward in adolescent mice is moderated by a complex interaction between social context and heritable differences in social motivation.
authors.affiliation: Department of Behavioral Neuroscience, Oregon Health and Science University, Mail Code L470, Rm 2182, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3011, USA.
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Kennedy
authors.forename: Jules B
authors.initials: JB
authors.lastname: Panksepp
authors.forename: Petra A
authors.initials: PA
authors.lastname: Runckel
authors.forename: Garet P
authors.initials: GP
authors.lastname: Lahvis
mesh_terms: D000367:Age Factors; D000818:Animals; D003213:Conditioning, Psychological / Q000187:drug effects*; D007398:Interpersonal Relations; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000494:pharmacology*; D009042:Motivation / Q000187:drug effects*; D011897:Random Allocation; D012934:Social Isolation
chemical_list: D009020:Morphine