Characterization of excitatory synaptic transmission in the retrosplenial cortex of adult mice

The retrosplenial cortex (RSC) plays an important role in navigation, memory and pain. However, there are few studies on excitatory synaptic transmission in the RSC. Here, we used a multi-electrode array recording system (MED64) to study the characteristics of excitatory synaptic transmission in the RSC and the contribution of different types of voltage-gated Ca²⁺ channels (VGCCs) in excitatory synaptic transmission. We found that glutamate is the major excitatory transmitter for RSC, and postsynaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors contribute to excitatory synaptic transmission. We also found that the N-type calcium channel blocker ω-conotoxin GVIA (ω-Ctx GVIA) had an inhibitory effect on basal synaptic transmission. The inhibitory effect was not consistent across channels, suggesting the actions effect of N-type VGCCs in RSC was inhomogeneous in spatial distribution. Our findings provide strong evidence that excitatory synaptic transmission in the RSC is mainly mediated by AMPA receptors and that N-type VGCCs mediate fast synaptic transmission in the RSC of adult mice.