Evidence that the relations between novelty-induced activity, locomotor stimulation and place preference induced by cocaine qualitatively depend upon the dose: a multiple regression analysis in inbred C57BL/6J mice.
It has been speculated that an individual's response to novelty is a reliable predictor of its vulnerability to develop addiction. However, the relationships between response to novelty and the development of drug-induced conditioned place preference are still unclear. The present study investigates the relationships between locomotor responses to novelty, cocaine-induced locomotor stimulation and conditioned place preference in C57BL/6J mice with multiple regression analyses. Four groups of mice receiving saline, 4, 8 or 12 mg/kg cocaine (i.p.) were submitted to an 8-day unbiased counterbalanced place conditioning protocol. Levels of locomotion on the pre-conditioning session were used as a score of locomotor response to a novel environment. The locomotor activity on the first cocaine-pairing session of the conditioning procedure served as a measure of the locomotion-activating response to a single injection of cocaine. Cocaine-induced dose-dependent locomotor stimulant effects and a significant place preference at all tested doses. A positive correlation was found between the locomotor responses to novelty and the locomotor stimulant effects of cocaine, but was significant only for the highest dose of cocaine (12 mg/kg). In contrast, there was a negative correlation between the locomotor response to novelty and the conditioned place preference induced by 4 mg/kg cocaine. Finally, the locomotor stimulant effects of cocaine do not correlate with cocaine-induced conditioned place preference at any tested dose of cocaine. The relationships between locomotor response to novelty and both cocaine-induced stimulant and rewarding effects can be differentially affected by the dose in inbred C57BL/6J mice.
Brabant
Christian
C
Département de Sciences Cognitives, Unité de Neurosciences Comportementales and Psychopharmacologie Expérimentale, Université de Liège, Boulevard du Rectorat Bt.32, B-4000 Liège, Belgium.
Quertemont
Etienne
E
Tirelli
Ezio
E
D000818:Animals; D003042:Cocaine / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004777:Environment; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000502:physiology*; D012044:Regression Analysis; D012201:Reward; D013268:Stimulation, Chemical
D003042:Cocaine