The Possible Role of Medial Prefrontal Cortex Beta-1-Adrenoceptors in Morphine-Induced Amnesia

The prelimbic region of the medial prefrontal cortex (mPFC) in the brain is crucial for memory. Norepinephrine elicits an important influence on mPFC functions. The stimulation of beta-adrenoceptors (beta-ARs) may play a critical role in the consolidation of long-term memory. The present study examines the possible role of beta(1)-ARs located in the mPFC on morphine-induced amnesia in rats. The animals were bilaterally implanted with chronic cannulas in the mPFC, trained in a step-through-type passive avoidance task and tested 24 h after training to measure step-through latency. Our present results indicated that posttraining intraperitoneal administration of morphine (2.5, 5 and 7.5 mg/kg) dose-dependently reduced the step-through latency. Different doses of xamoterol (0.01, 0.1 and 1 mu g/rat) have shown no significant change in the step-through latency, but posttraining intram-PFC microinjection of atenolol (0.2 and 0.4 mu g/rat) had an amnesic effect. Moreover, atenolol-caused amnesia was reversed by an ineffective dose of xamoterol (0.1 mu g/rat). On the other hand, coadministration of an ineffective dose of atenolol (0.1 mu g/rat) with an ineffective dose of morphine (2.5 mg/kg) induced an amnesic effect. Meanwhile, xamoterol had no effect on morphine-induced amnesia. These results suggest that beta(1)-ARs of the prelimbic region in the mPFC may play an important role in morphine-induced amnesia. (C) 2014 S. Karger AG, Basel