The role of acetylcholine muscarinic receptors in the rat basolateral amygdala on morphine-induced place preference

Some studies have shown that acetylcholine muscarinic receptors involved in the opiate reward. In the present study, the effect of intra-basolateral amygdale (BLA) acetylcholine muscarinic like receptor agonist (physostigmine) and antagonist (atropine) on the acquisition of morphine-induced place preference has been investigated in male Wistar rats. For this purpose, two 22 gauges guide cannulae were implanted into the BLA by using a sterotaxic instrument. After 7 days using biased method and the subcutaneous administration of morphine or intra-BLA injection of acetylcholinergic agents, the induction of conditioned place preference (CPP) was examined. Subcutaneous administration of the different doses of morphine sulfate (0.5-10 mg/kg) produced a significant CPP dose-dependently. The intra-BLA injection of physostigmine (1, 3, and 5 µg/rat) significantly potentiated the acquisition of morphine (0.5 mg/kg)-induced place preference. This potentiation reversed by atropine (7 µg/rat) pretreatment. The intra-BLA injection of different doses of atropine (1, 4, and 7 µg/rat) significantly reduced the acquisition of morphine (7.5 mg/kg)-induced place preferenc. Physostigmine or atropine by itself did not produce reliable CPP. Our studies demonstrated for the first time that acetylcholine muscarinic receptors in BLA have an important role in the acquisition of morphine-induced place preference.