Spike Properties of Granule Retrosplenial Cortex L2/3 Neurons

The retrosplenial cortex (RSC) is reciprocally connected with various brain regions, including the visual cortex (van Groen & Wyss, J Comp Neurol, 2003), the hippocampus (Wyss et al., Hippocampus, 1992), the medial entorhinal cortex, and the post subiculum, etc. (Todd & Bucci, Neural Plasticity, 2015). The RSC is implicated to participate in spatial memories, head direction (S. D. Vann et al, Behavioural Brain Research, 2014) and context fear memories with interval delays (Kwapis et al., Neurobiol Learn Mem. 2015). However, the basic mechanisms and properties underlying its involvement in the behaviors are largely unknown. A previous report has demonstrated that small pyramidal cells in the layer 2/3 of the rat RSC exhibit late-spiking properties due to a series of Kv channel subtypes (Kurotani et al, Brain Structure and Function, 2013), but how these features influence the transmission among RSC neurons and serve for higher-level interactions remain unclear. Here, we first examined the specific spiking properties of RSC layer 2/3 neurons using whole cell patch clamp recordings. After a brief current injection, these neurons showed a shorter spike latency, which is different from other brain regions we tested, including the RSC layer 5/6, the anterior cingulate layer 2/3, and the hippocampal CA1 area. This phenomenon is attenuated when the prior current injection became shorter, weaker, or more apart from the stimulation. We will also conduct extra-cellular stimulation using bipolar electrode as well as optogenetic tools to further examine the special role of these features in the integration of information flow.