Strain differences in the effects of adrenalectomy on the midbrain dopamine system: implication for behavioral sensitization to cocaine
Abstract
Adrenalectomy (ADX) abolishes behavioral sensitization to cocaine in DBA/2, but not C57BL/6 inbred mice. The present study tests the hypothesis that this ADX effect on behavioral sensitization in the DBA/2 strain involves changes in midbrain dopamine systems that do not occur in the C57BL/6 strain. For that purpose, we have measured tyrosine hydroxylase (TH) and dopamine transporter (DAT) mRNA and D1- and D2-like receptor binding in C57BL/6 and DBA/2 mice that were i) unoperated, ii) ADX or sham (SHAM) operated, or iii) ADX or SHAM operated and subjected to a cocaine sensitization regimen (15.0 mg/kg cocaine on nine consecutive days, followed by a 7.5 mg/kg challenge after a 5-day withdrawal). ADX prevented behavioral sensitization to cocaine in the DBA/2, but not the C57BL/6 strain [de Jong IEM, Oitzl MS, de Kloet ER (2007) Adrenalectomy prevents behavioural sensitisation of mice to cocaine in a genotype-dependent manner. Behav Brain Res 177:329-339]. Mice were killed under basal conditions, in the latter case 24 h after the cocaine challenge. ADX did not affect the dopaminergic markers in drug naïve mice. By contrast, strain-dependent neuroadaptations were found in the midbrain dopamine system of mice subjected to the sensiti...Continue Reading
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