Formation of aversive memories associated with conditioned drug withdrawal requires BDNF expression in the amygdala in acute morphine-dependent rats.

Aim: Brain-derived neurotrophic factor (BDNF) plays an important role in learning and memory in multiple brain areas. In the present study, we investigated the roles of BDNF in aversive memories associated with conditioned drug withdrawal in acute morphine-dependent rats.

Methods: Conditioned place aversion (CPA) was induced in male SD rats exposed to a single dose of morphine (10 mg/kg, sc) followed by naloxone (0.3 mg/kg, sc). In some rats, BDNF receptor antagonist K252a (8.5 ng per side) or BDNF scavenger TrkB-FC (0.65 μg per side) was bilaterally microinjected into amygdala before naloxone injection. BDNF mRNA and protein expression levels in amygdala were detected after the behavior testing.

Results: CPA behavior was induced in rats by the naloxone-precipitated morphine withdrawal, which was accompanied by significantly increased levels of BDNF mRNA and protein in the amygdala. Bilateral microinjection of TrkB-FC or K252a into the amygdala completely blocked CPA behavior in the rats.

Conclusion: Formation of aversive memories associated with conditioned drug withdrawal in acute morphine-dependent rats requires BDNF expression in the amygdala.