behavior/neurological
• repeated 20 mg/kg cocaine treatment does not induce behavioral sensitization in mutants, in contrast to wild-type; sensitized grooming behavior develops to similar extent in mutant and wild-type animals
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• mutants exhibit more persistent memory for reinforcing effects of cocaine than wild-type mice
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• cocaine-induced conditioned place preference behavior does not extinguish until 22 days of training compared to 12 (and 16) days of training in wild-type
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• 20 mg/kg cocaine treatment induces rearing in controls and mutants, but mutants show lower activity than controls; with repeated injections, wild-type mice develop sensitized rearing but mutants do not
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nervous system
• repeated cocaine injections increase dendritic spine density on medium spiny neurons in the nucleus accumbens and caudate putamen of wild-type mice, but mutant brains show lower spine densities
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• repeated cocaine injections increase the number of dendrites in the cortex of wild-type mice, but mutants have significantly lower dendritic number
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