Withdrawal from extended‐access cocaine self‐administration results in dysregulated functional activity and altered locomotor activity in rats

Abstract

Much work has focused on determining the consequences of cocaine self-administration on specific neurotransmitter systems, thus neglecting the global changes that occur. Previous imaging studies have focused on the effects of cocaine self-administration in the presence of high blood levels of cocaine, but have not determined the functional effects of cocaine self-administration after cocaine has cleared. Extended-access cocaine self-administration, where animals administer cocaine for 6h each day, results in escalation in the rate of cocaine intake and is believed to model the transition from recreational use to addiction in humans. We aimed to determine the functional changes following acute (48h) withdrawal from an extended-access, defined-intake self-administration paradigm (5days, 40 injections/day, 6h/day), a time point when behavioral changes are present. Using the 2-[(14) C]deoxyglucose method to measure rates of local cerebral glucose metabolism, an indicator of functional activity, we found reductions in circuits related to learning and memory, attention, sleep, and reward processing, which have important clinical implications for cocaine addiction. Additionally, lower levels of functional activity were found in the dorsal raphe and locus coeruleus, suggesting that cocaine self-administration may have broader effects on brain function than previously noted. These widespread neurochemical reductions were concomitant with substantial behavioral differences in these animals, highlighted by increased vertical activity and decreased stereotypy. These data demonstrate that behavioral and neurochemical impairments following cocaine self-administration are present in the absence of drug and persist after cocaine has been cleared.