LESIONS OF THE LATERAL PARABRACHIAL NUCLEUS BLOCK THE AVERSIVE MOTIVATIONAL EFFECTS OF BOTH MORPHINE AND MORPHINE-WITHDRAWAL BUT SPARE MORPHINES DISCRIMINATIVE PROPERTIES

This study examined if the aversive properties of morphine, the aversi ve properties of morphine withdrawal, and the discriminative propertie s of morph inc are mediated by common neurobiological substrates. Lesi ons of the lateral parabrachial nucleus, which blocked the aversive pr operties of morphine in the conditioned taste aversion paradigm, also blocked the acquisition of conditioned place aversions to environments paired with the aversive properties of morphine withdrawal in morphin e-dependent rats. When morphine and saline were used as cues in a disc rimination task, however, both sham-operated and lesioned rats were ab le to solve the task.