Oral cocaine seeking by rats: action or habit?
Having established that the presence of cocaine in a 10% (wt/vol) sucrose solution enhanced the reinforcing properties of the solution in a dose-dependent manner, the authors investigated the susceptibility of oral cocaine seeking to outcome devaluation. Rats were trained to perform different instrumental responses for a cocaine-sucrose and a lemon-sucrose solution. An aversion was then conditioned from either the cocaine-sucrose or the lemon-sucrose solution by pairing consumption with lithium chloride. When instrumental performance was subsequently tested in extinction, the rats performed the lemon-sucrose response less if this solution, rather than cocaine-sucrose, had been devalued by aversion conditioning. By contrast, performance of the cocaine-sucrose response was unaffected by whether the cocaine-sucrose or the lemon-sucrose solution had been devalued.