Functional cross-excitation between afferent A- and C-neurons in dorsal root ganglia.
Electrophysiological recordings were made in vitro from primary afferent neurons with unmyelinated axons (C-neurons) in excised rat dorsal root ganglia. Spike activity triggered in neurons with myelinated axons (A-neurons) by stimulation of the peripheral nerve or the dorsal root produced a transient depolarization in passive neighboring C-neurons that share the same ganglion. About 90% of neurons sampled responded with this "cross-depolarization". Cross-depolarization was associated with functional excitation as indicated by an increase in firing probability in response to previously subthreshold intracellular test pulses. Furthermore, it yielded a net increase of the input resistance of the affected C-neurons. We suggest that functional coupling among DRG neurons could serve a metabolic role, providing a functionally relevant feedback signal useful for controlling the excitability of nociceptive sensory endings. In addition, the results provide a novel mechanism whereby afferent nociceptors could be stimulated by activity in low-threshold mechanoreceptors, particularly in the event of nerve injury. Hence, the coupling between afferent A- and C-neurons in dorsal root ganglia provides a novel candidate mechanism for neuropathic pain.
Amir
R
R
Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Israel.
Devor
M
M
D000818:Animals; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology*; D008297:Male; D009412:Nerve Fibers / Q000502:physiology*; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains