title: Inhibition of dopamine efflux in the rat nucleus accumbens during abstinence after free access to d-amphetamine.
abstract: Abstinence following 'binge' use of psychostimulants is hypothesized to be related to a depletion of synaptic dopamine (DA) in the nucleus accumbens. The present study, therefore, tested the pharmacological responsiveness of the mesolimbic DA system to d-amphetamine injections, measured by in vivo chronoamperometry with stearate-modified graphite paste electrodes, during voluntary abstinence when rats were given prolonged free availability to d-amphetamine. Rats self-administered i.v. d-amphetamine (FR-1 time out 30 s; 0.25 mg/kg per inf) in three sessions, each separated by approximately 24 h, (1) to a criterion of 12 infusions; (2) for 24 h and (3) for 48 h. During the third session, when self-administration had ceased for at least 1.5 h (abstinence), and DA levels were near, or below, pre-drug baseline values, rats received passive i.v. injections of d-amphetamine or vehicle in a pattern that mimicked self-administration patterns during the first hour of the 48 h session. In contrast to the significant increases in DA efflux observed during the first hour of self-administration, d-amphetamine injections during abstinence did not increase DA oxidation currents. Furthermore, the length of the abstinence period was correlated with the time required for DA to return to pre-abstinence values. Together, these results suggest that the mesolimbic DA system is pharmacologically unresponsive to the actions of d-amphetamine during abstinence, and that resumption of drug use is associated with 'recovery of function' in the mesolimbic DA system.
authors.affiliation: Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK.
authors.forename: Patricia
authors.initials: P
authors.lastname: Di Ciano
authors.forename: Charles D
authors.initials: CD
authors.lastname: Blaha
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Phillips
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003216:Conditioning, Operant / Q000187:drug effects; D003913:Dextroamphetamine / Q000009:adverse effects*; D004298:Dopamine / Q000378:metabolism*; D018765:Dopamine Uptake Inhibitors / Q000009:adverse effects*; D004563:Electrochemistry; D007275:Injections, Intravenous; D008297:Male; D009714:Nucleus Accumbens / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D020318:Rats, Long-Evans; D012646:Self Administration; D013238:Stereotaxic Techniques; D013375:Substance Withdrawal Syndrome / Q000378:metabolism*
chemical_list: D018765:Dopamine Uptake Inhibitors; D003913:Dextroamphetamine; D004298:Dopamine