Using two-photon Ca2+ imaging to reveal spinal cord dorsal horn networks

Abstract

The spinal cord dorsal horn is a key area for the processing of sensory information such as pain, heat, cold, touch and itch. Our understanding of spinal cord microcircuitry has proved difficult, in part, due to a lack of effective tools to allow identification of dorsal horn neuron populations and how they are connected. A recent technique developed in our lab using pharmacology-based profiling (termed CICADA) has allowed us to visualize eight populations of excitatory neurons in the superficial dorsal horn. Here, we use two-photon Ca2+ imaging and CICADA to tease apart connectivity across these CICADA-defined populations. Through back labeling spinoparabrachial projection neurons, we also identify spinal output neurons, and the spinal networks that provide input onto these cells. These experiments reveal the network connectivity, including the spinal output neurons, that are downstream of each CICADA-defined population. Together, these findings provide new insight into the connectivity in the superficial dorsal horn. Grant support from 2R01 NS096705-06.