Neither non-contingent electric footshock nor administered corticosterone facilitate the acquisition of methamphetamine self-administration

Abstract

Previous research has indicated a role for the hypothalamo–pituitary–adrenal (HPA) axis in the acquisition of intravenous cocaine self-administration since both exposure to stressors and exogenous injections of corticosterone facilitate this behavior. The present experiment was designed to determine whether electric footshock or pretreatment with corticosterone would produce similar effects on the acquisition of methamphetamine self-administration in male Wistar rats. Following initial food training, the rats were allowed to self-administer methamphetamine in ascending doses (0.0075–0.12 mg/kg/infusion) that were doubled weekly. Neither non-contingent electric footshock nor treatment with corticosterone (2.0 mg/kg, i.p.) affected the lowest dose at which the rats first acquired methamphetamine self-administration (0.015 mg/kg/infusion). The treatment groups all had similar inverted “U”-shaped acquisition curves typical of psychostimulants. Although these experiments do not indicate a major role for the HPA axis in the acquisition of methamphetamine self-administration, more studies need to be conducted to further evaluate the effects of the HPA axis on the acquisition of methamphetamine self-administration before a potential role can be ruled out.