Changed morphine sensitivity of morphine-dependent rats after laser exposure of the cerebral prefrontal cortex

We studied the effect of bilateral laser exposure of the cerebral prefrontal cortex in morphine-dependent rats on their sensitivity to positive reinforcing and toxic effect of morphine. Laser exposure led to partial deafferentation of the cingulum. Exposure of the anterior and central areas of the prefrontal cortex stimulated self-administration of low morphine doses and had no effect on self-administration of high concentrations. Exposure of the posterior area of the prefrontal cortex did not appreciably change self-administration of medium and low morphine doses, but self-administration of high doses significantly increased. Exposure of the anterior area of the prefrontal cortex significantly decreased the sensitivity to the positive reinforcing effect of morphine. Exposure of the posterior prefrontal cortex decreased the sensitivity to the toxic effect of morphine.