BDNF-dependent signaling in the olfactory bulb modulates social recognition memory in mice

An operative olfactory bulb (OB) is critical to social recognition memory (SRM) in rodents, which involves identifying conspecifics. Furthermore, OB also allocates synaptic plasticity events related to olfactory memories in their intricate neural circuit. Here, we asked whether the OB is a target for brain-derived neurotrophic factor (BDNF), a well-known mediator of plasticity and memory. Adult ICR-CD1 male mice had their SRM evaluated under the inhibition of BDNF-dependent signaling directly in the OB. We also quantified the expression of BDNF in the OB, after SRM acquisition. Our results presented an amnesic effect of anti-BDNF administered 12 h post-training. Although the western blot showed no statistical difference in pro-BDNF and BDNF expression, the analysis of fluorescence intensity in slices suggests SRM acquisition decreases BDNF in the granular cell layer of the OB. Next, to test the ability of BDNF to rescue SRM deficit, we administered the human recombinant BDNF (rBDNF) directly in the OB of socially isolated (SI) mice. Unexpectedly, rBDNF did not rescue SRM in SI mice. Furthermore, BDNF and pro-BDNF expression in the OB was unchanged by SI. Our study reinforces the OB as a plasticity locus in memory-related events. It also adds SRM as another type of memory sensitive to BDNF-dependent signaling.