Differential effects of quinolinic acid lesions of the medial prefrontal cortex on the expression of morphine- and dizocilpine-induced behavioural plasticity in the rat

Development and expression of behavioural sensitization have been shown to be differentially affected by drugs and lesions. Here we assessed the effec ts of quinolinic acid lesions of the rat medial prefrontal cortex on the ex pression of enhanced locomotion and rearing that has been induced prior to the lesions by 14 daily injections of morphine (10 mg/kg), dizocilpine (MK- 801) (0.3 mg/kg) or the combination of both drugs. Expression of tolerance to morphine-induced behavioural inhibition was blocked by the lesions while the expression of MK-801 -induced sensitization was not affected and the e xpression of the sensitization induced by the drug combination was only mil dly attenuated. These results suggest that the expression of behavioural pl asticity induced by different drugs is mediated at least in part by differe nt neural substrates. (C) 2000 Elsevier Science Ireland Ltd. All rights res erved.