Slow chemical transmission between dorsal root ganglion neuron somata

Somatic sensory neuron somata are located within the dorsal root ganglia (DRG) and are mostly ensheathed by individual satellite glial cell sheets. It has been noted, however, that a subpopulation of these DRG somata are intimately associated, separated only by a single thin satellite glial cell membrane septum. We set out to test whether such neuron–glial cell–neuron trimers (NGlNs) are also linked functionally. The presence of NGlNs in chick DRGs was confirmed by electron microscopy. Selective satellite glial cell immunostains were identified and were used to image the inter‐neuron septa in DRG frozen sections. We used a gentle, dispase‐based enzymatic method to isolate chick and rat NGlNs in vitro for double patch clamp recordings. In the majority of pairs tested, an action potential‐like stimulus train delivered to one soma resulted in a delayed, noisy and long‐duration response in its idle partner. The response to a second stimulus train given minutes later was markedly facilitated. Both bidirectional and unidirectional transmission was observed between the paired neurons. Transmission was chemical and block by the general purinergic blocker suramin implicated ATP as a neurotransmitter. We conclude that the two neuronal somata in the NGlN can communicate by chemical transmission, which may involve a transglial, bi‐synaptic pathway. This novel soma‐to‐soma transmission reflects a novel form of processing that may play a role in sensory disorders in the DRG and interneuron communication in the central nervous system. Sensory neuron cell bodies in the Dorsal Root Ganglion provide axons that link peripheral sense organs to the central nervous system. These neurons are generally believed to be isolated by glial cells and to lack direct neuron‐to‐neuron signaling. We show that a sub‐set of DRG neurons, that abut closely and are separated by a single common glial cell, exhibit slow transmission. This signaling may play a role in sensory processing or contribute to ganglion trophic modulation or development.