SV2A is largely expressed in inhibitory neurons while SV2B is predominately expressed in excitatory neurons.

<p>(A) Cultured cortical neurons were exposed to the indicated concentrations of TeNT for 3 minutes in high K⁺ buffer then returned to the incubator for 2 days. mEPSCs and mIPSCs were analyzed and the frequency of mEPSCs was reduced to a greater degree than mIPSCs. mEPSC/mIPSC at 0 pM TeNT, n = 10; mEPSC at 0.5 pM TeNT, n = 10; mIPSC at 0.5 pM TeNT, n = 9; mEPSC/mIPSC at 5 pM TeNT, n = 8; error bars represent SEM. (B) Sample traces of dissociated spinal cord neurons exposed to TeNT (50 pM) in high K⁺ buffer, washed than analyzed after 3 hours. Cultures treated with TeNT exhibited pronounced hyper excitability, as evidenced by high-frequency bursting activity, as compared to control neurons. (C) Representative images of SV2A/B staining with markers for excitatory (vGLUT1/2) or inhibitory (vGAT) boutons in cortical neurons and spinal cord slices. Red boxes indicate the region that was subjected to analysis by immunocytochemistry. (D) Pearson's coefficient for SV2A/B localization with excitatory/inhibitory terminals. In cortical neurons, SV2A localizes to inhibitory terminals while SV2B localizes to excitatory terminals. In contrast, in spinal cord slices, SV2A showed a greater degree of colocalization with markers for inhibitory terminals than excitatory terminals, while SV2B largely localized to excitatory terminals. Error bars represent SEM, SV2A cortical neurons n = 4, SV2B cortical neurons n = 6, spinal cord slice n = 13, *p<0.05, ***p<0.001.