Adenosine triphosphate-evoked currents in cultured dorsal root ganglion neurons obtained from rat embryos: desensitization kinetics and modulation of glutamate release.

Sensory neurons express purinergic P2X receptors on their central and peripheral terminals as well as their cell bodies. ATP activation of these receptors drives action potential firing and glutamate release with potentially important consequences for sensory function. Here we show ATP-gated currents activated in cultured embryonic dorsal root ganglion neurons have heterogeneity of time-courses comparable to those observed in different subpopulations of acutely dissociated adult dorsal root ganglion neurons. The distribution of time-courses across the population of cultured neurons is strongly influenced by culture conditions. Heterogeneity in ATP current kinetics occurs even though immunocytochemical staining reveals a relatively homogeneous and widespread expression of the P2X2 and P2X3 subunits. We show that the time-courses of ATP-gated currents recorded at the cell bodies are mirrored by the time-courses of transmitter release from the dorsal root ganglion nerve terminals, indicating similar P2X receptor properties on the soma and their associated terminals. Our results illustrate a functional heterogeneity of P2X receptor-mediated currents that is strongly influenced by external factors. This heterogeneity in current kinetics may have implications for neuronal function as it constrains the time-course of ATP-mediated modulation of neurotransmitter release at sensory nerve terminals.