The Combined Effects of Corticosterone and Brain-Derived Neurotrophic Factor on Plasticity-Related Receptor Phosphorylation and Expression at the Synaptic Surface in Male Sprague-Dawley Rats.

Following acute exercise, a temporal window exists wherein neuroplasticity is thought to be heightened. Although a number of studies have established that pairing this post-exercise period with motor training en-hances learning, the mechanisms through which exercise-induced priming occurs are not well understood. Previously, we characterized a rodent model of acute exercise that generates significant enhancement in glu-tamatergic receptor phosphorylation as a possible mechanism to explain how exercise-induced priming might occur. However, whether these changes are stimulated by peripheral factors (e.g., glucocorticoids), central ef-fects (e.g., brain-derived neurotrophic factor (BDNF), or a combination of the two remains unclear. Herein, we explored the possible individual and/or cumulative contribution corticosterone (CORT) and BDNF may have on glutamate receptor phosphorylation and synaptic surface expression. Tissue slices from the sensorimotor cortex were prepared and acutely (30 min) incubated with either CORT (200 nM), BDNF (20 ng/mL), or the simulta-neous application of CORT and BDNF (CORT+BDNF). Immunoblotting with biotinylated synaptoneurosomes (which provide an enrichment of proteins from the synaptic surface) suggested divergent effects between CORT and BDNF. Acute CORT application enhanced NMDA-(GluN2A, B) and AMPA-(GluA1) receptor phosphoryla-tion, whereas BDNF preferentially increased synaptic surface expression of both NMDA-and AMPA-receptor subunits. The combined effects of CORT+BDNF resulted in a unique subset of signaling patterns that favored phosphorylation in the absence of surface expression. Taken together, these data provide a mechanistic frame-work for how CORT and BDNF may alter glutamatergic synapses during exercise-induced priming.