The Role of GABAB Receptors in Morphine Self-Administration

BACKGROUND: There is only little information about the effects of GABA receptors agonist and antagonist on morphine self-administration. Present study was designed to assess role of GABAB receptors in the regulation of morphine-reinforced self-administration. METHODS: This study was performed in four groups of rats: (1) Saline group, which received saline in the self-administration session. (2) Morphine group, which received morphine in saline solution in the self-administration session. (3) Baclofen + Morphine group, which received both baclofen 20 min before self- administration test and morphine in the self-administration session. (4) Phaclofen + Morphine group, which received both phaclofen 20 min before self- administration test and morphine in the self-administration session. The number of lever pressing and self-infusion were recorded. RESULTS: Morphine significantly increased the number of active lever pressing dose dependently in self-administration session in comparative with saline group. Administration of baclofen, 20 min before morphine self-administration produced significant decrease in the initiation of morphine self-administration during all session. Conversely, pre-treatment of phaclofen increased the number of active lever pressing and self-infusion in this test. CONCLUSION: Our results indicated a short-term treatment by baclofen, reduced morphine-maintenance response in a dose-dependent manner, suggesting that GABAB receptor agonists could be useful for reversing the neuroadaptations related to opiates.