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Original Article

Exp Neurobiol 2014; 23(1): 53-64

Published online March 30, 2014

© The Korean Society for Brain and Neural Sciences

Attenuated Glial K+ Clearance Contributes to Long-Term Synaptic Potentiation Via Depolarizing GABA in Dorsal Horn Neurons of Rat Spinal Cord

Jaekwang Lee1,3, Oleg V Favorov1, Mark Tommerdahl1, C. Justin Lee3,4* and Barry L. Whitsel1,2*

1Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA, 2Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA, 3WCI Center for Functional Connectomics, Institute of Science and Technology (KIST), Seoul, Korea, 4KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, Korea

Correspondence to: *To whom correspondence should be addressed.
C. Justin Lee
TEL: 82-2-958-6940, FAX: 82-2-958-6937
Barry L. Whitsel
TEL: 1-919-966-1291, FAX: 1-919-966-6927

Received: March 2, 2014; Revised: March 5, 2014; Accepted: March 5, 2014


It has been reported that long-term enhancement of superficial dorsal horn (DHs) excitatory synaptic transmission underlies central sensitization, secondary hyperalgesia, and persistent pain. We tested whether impaired clearance of K+ and glutamate by glia in DHs may contribute to initiation and maintenance of the CNS pain circuit and sensorimotor abnormalities. Transient exposure of the spinal cord slice to fluorocitrate (FC) is shown to be accompanied by a protracted decrease of the DHs optical response to repetitive electrical stimulation of the ipsilateral dorsal root, and by a similarly protracted increase in the postsynaptic response of the DHs like LTP. It also is shown that LTPFCdoes not occur in the presence of APV, and becomes progressively smaller as [K+]o in the perfusion solution decreased from 3.0 mM to 0.0 mM. Interestingly LTPFC is reduced by bath application of Bic. Whole-cell patch recordings were carried out to evaluate the effects of FC on the response of DHs neurons to puffer-applied GABA. The observations reveal that transient exposure to FC is reliably accompanied by a prolonged (>1 hr) depolarizing shift of the equilibrium potential for the DHs neuron transmembrane ionic currents evoked by GABA. Considered collectively, the findings demonstrate that LTPFC involves (1) elevation of [K+]o in the DHs, (2) NMDAR activation, and (3) conversion of the effect of GABA on DHs neurons from inhibition to excitation. It is proposed that a transient impairment of astrocyte energy production can trigger the cascade of dorsal horn mechanisms that underlies hyperalgesia and persistent pain.

Keywords: dorsal horn, astrocytes, glia-neuron interactions, central sensitization, hyperalgesia, persistent pain