Post-training intra-basolateral amygdala infusions of norepinephrine block sevoflurane-induced impairment of memory consolidation and activity-regulated cytoskeletal protein expression inhibition in rat hippocampus

Considerable evidence indicates that the noradrenergic system of the basolateral amygdala (BLA) participates in the consolidation of various types of emotionally arousing memories. We previously reported that administration of an anesthetic-dose of sevoflurane immediately after continuous multiple-trail inhibition avoidance (CMIA) training impaired memory consolidation. This experiment investigated whether posttraining noradrenergic activation of the BLA is sufficient to reverse the memory impairing effect of sevoflurane. Adult male Sprague-Dawley rats received bilateral injections of norepinephrine (NE 0.3, 1.0, or 3.0 μg/0.5 μl) or normal saline (NS 0.5 μl) immediately after training in a CMIA paradigm. Subsequently, the rats were exposed to sevoflurane (2% inspired) or air for 2. h. Norepinephrine produced a dose-dependent enhancement of memory consolidation on a 24-h retention test. The highest dose of NE tested (3.0 μg/0.5 μl) blocked sevoflurane-induced impairment of memory consolidation and reversed the inhibitory effect of sevoflurane on activity-regulated cytoskeletal protein (Arc) expression in the hippocampus 2. h after training. These findings provide evidence that the mechanism mediating the memory-impairing effect of sevoflurane involves a network interaction between the BLA noradrenergic system and modulation of Arc protein expression in the hippocampus.