Effects of the social conditions of housing through testing on cocaine-induced contextual sensitisation and conditioned locomotion in C57BL/6J mice.
The potential differential effects of isolated and collective housing through the testing phase on sensitisation to cocaine-induced locomotion, the subsequent conditioned locomotion and the context-dependent expression of sensitisation were examined in C57Bl/6J male mice. Sensitisation was first generated in mice receiving seven once-daily subcutaneous injections of either saline or 10 mg/kg cocaine, before being placed in a testing chamber (singly) or in their home cage. On Day 8, mice were tested for conditioned locomotion (under saline). On Day 12, after three daily sessions of reinstatement of sensitisation, they were tested for contextual sensitisation (under cocaine). Whereas little or no effect of housing on the development of sensitisation was found, postsensitisation conditioned activity was significantly greater in isolation-kept mice (in comparison with the group-kept animals) and the likelihood of inducing a context-dependent expression of sensitisation was greater in grouped-housed mice. The results indicate that some of the aspects of contextual sensitisation can be influenced by the social conditions of lodging, not only when these conditions start several weeks before or during previous developmental periods of animals life (as previously published), but also when social isolation or social grouping are initiated after sexual maturity and applied through the period of treatments and testing. Moreover, the differential effect of social conditions of lodging on conditioned activity and contextual expression of sensitisation disagrees with the excitatory conditioning account of contextual sensitisation.
Michel
Anne
A
Université de Liège, Département des Sciences Cognitives, Laboratoire de Neuroscience Comportementale et de Psychopharmacologie Expérimentale, Boulevard du Rectorat B-32, B-4000 Liège, Belgium.
Tirelli
Ezio
E
D000818:Animals; D003042:Cocaine / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000187:drug effects*; D012931:Social Environment; D012934:Social Isolation
D003042:Cocaine