Drug addiction is a progressive, chronic brain disorder that ravages the health and lives of people globally. In the last century, pioneering discoveries in addiction science have begun to put to rest misconceptions concerning the nature of addiction and to yield new breakthroughs, which are poised to revolutionize its prevention and treatment. Importantly, addiction is now recognized as a disordered integration of cognitive and motivational aspects of reward-directed behavior involving higher order limbic-corticostriatal structures (Kalivas and Volkow, 2005). The medial prefrontal cortex (mPFC) and associated circuits are particularly sensitive to plasticity incurred due to repeated pairing of environmental stimuli (eg, drug paraphernalia, etc) with exposure to abused drugs. These associations between environmental cues and drug-taking are essential drug-associated memories that can trigger conditioned emotional responses in addicts and ‘craving’ (desire for drug), oft cited to explain relapse to drug-seeking and drug-taking during abstinence.

The cortical control of drug-seeking is the focus of a new study by Janet Neisewander and her colleagues reported in Neuropsychopharmacology (Pentkowski et al, 2010). These studies concentrate on cocaine dependence; cocaine abuse spirals to addiction in upwards of 15% of cocaine users and limited therapeutic options to suppress recidivism are available. Pentkowski et al (2010) have uncovered a nuanced neural circuit that selectively restrains the frontocortical circuitry that controls drug-seeking behavior in rats. In the procedure employed here, intravenous catheters were surgically implanted and rats were trained to lever press to deliver an intravenous injection of cocaine plus several associated environmental cues (ie, light and tone, sound of infusion pump). Following training of the cocaine self-administration, rats were subjected to extinction during which lever presses did not result in administration of cocaine or the associated cues. Subsequent to extinction, rats were given an injection of cocaine or were presented with the cue stimuli, previously associated with cocaine delivery, either of which then ‘reinstated’ cocaine-seeking. This cocaine-seeking in rats parallels the experience of an abstinent cocaine addict exposed to either a dose of cocaine or the environment in which cocaine use occurred. These exposures often result in relapse, which cycles into a loss of behavioral control and habitual drug use. This self-administration/reinstatement model employed in preclinical studies of cocaine abuse and addiction provides a valid method to explore the neural mechanisms and circuitry underlying cocaine-seeking and cocaine-taking.

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