Lack of effect of habenula lesion on heroin self-administration in rats.

We examined the effects of bilateral electric lesion of the habenula (Hb) on the acquisition and maintenance of heroin self-administration. The rats were trained to self-administer heroin (0.05 mg/kg/infusion) under FR1 schedule in daily 4h sessions. A progressive ratio schedule (PR3-4) was used to evaluate the relative motivational value of heroin reinforcement. Compared with the controls, neither pre-training nor post-training of Hb lesions had any effects on the total amount of infusions and motivational value of heroin reward. However, pre-training Hb lesion caused transient active and inactive nose-poke responding in the early phase of training, suggesting increased locomotor exploration. The results suggest that Hb might not play an important role in mediating the acute reinforcing effect of heroin.