The Single Dose Cocaine Reinstatement of Lever‐Pressing Behavior in Rats is Explained by The Compulsion Zone Theory

Abstract

The compulsion zone theory of the cocaine self‐administration paradigm states that lever‐pressing behavior is induced when cocaine levels fall to or below the satiety threshold. Single injections of cocaine are known to reinstate lever‐pressing in rats trained to self‐administer cocaine. We investigated whether this phenomenon can be explained by the compulsion zone theory. Male Sprague‐Dawley rats (n = 5) were trained to self‐administer cocaine i.v. on an FR‐1 schedule. Once trained, these rats were administered a single dose of cocaine (2 – 12 µmol/kg, i.v.) in four daily sessions per week, and the time to lever‐pressing, the number of presses and the duration of pressing were recorded. The latency from the start of an injection to the resumption of lever pressing increased with the cocaine dose and ranged from approximately 2 min at 2 µmol/kg to more than 15 min at 12 µmol/kg. The D1 dopamine receptor antagonist SCH23390 (10‐30 nmol/kg i.v.) decreased the latency to reinstatement of lever pressing, following a dose of 12 µmol/kg cocaine. The increasing latency to lever‐pressing is consistent with the increasingly higher cocaine levels taking longer to fall to the satiety threshold, while the lower doses are immediately within the compulsion zone. An antagonist‐induced elevation of the satiety threshold explains the reduced latency to reinstatement. The number and duration of lever presses may reflect the time that the cocaine levels are within the compulsion zone. The cocaine satiety threshold model explains the dose‐dependent delay in reinstatement of lever‐pressing behavior and the effect of dopamine antagonists.