The possible role of medial prefrontal cortex beta-1-adrenoceptors in morphine-induced amnesia.

PMID 25096537


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 β-adrenoceptors (β-ARs) may play a critical role in the consolidation of long-term memory. The present study examines the possible role of β₁-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 µg/rat) have shown no significant change in the step-through latency, but posttraining intra-mPFC microinjection of atenolol (0.2 and 0.4 µg/rat) had an amnesic effect. Moreover, atenolol-caused amnesia was reversed by an ineffective dose of xamoterol (0.1 µg/rat). On the other hand, coadministration of an ineffective dose of atenolol (0.1 µg/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 β₁-ARs of the prelimbic region in the mPFC may play an important role in morphine-induced amnesia.