Serotonin 5-HT_2C receptor protein expression is enriched in synaptosomal and post-synaptic compartments of rat cortex

The action of serotonin (5-HT) at the 5-HT_2C receptor (5-HT _2CR) in cerebral cortex is emerging as a candidate modulator of neural processes that mediate core phenotypic facets of several psychiatric and neurological disorders. However, our understanding of the neurobiology of the cortical 5-HT_2CR protein complex is currently limited. The goal of the present study was to explore the subcellular localization of the 5-HT _2CR in synaptosomes and the post-synaptic density, an electron-dense thickening specialized for post-synaptic signaling and neuronal plasticity. Utilizing multiples tissues (brain, peripheral tissues), protein fractions (synaptosomal, post-synaptic density), and controls (peptide neutralization, 5-HT_2CR stably-expressing cells), we established the selectivity of two commercially available 5-HT_2CR antibodies and employed the antibodies in western blot and immunoprecipitation studies of prefrontal cortex (PFC) and motor cortex, two regions implicated in cognitive, emotional and motor dysfunction. For the first time, we demonstrated the expression of the 5-HT_2CR in post-synaptic density-enriched fractions from both PFC and motor cortex. Co-immunoprecipitation studies revealed the presence of post-synaptic density-95 within the 5-HT_2CR protein complex expressed in PFC and motor cortex. Taken together, these data support the hypothesis that the 5-HT_2CR is localized within the post-synaptic thickening of synapses and is therefore positioned to directly modulate synaptic plasticity in cortical neurons.