Elsevier

Neuroscience Letters

Volume 255, Issue 3, 23 October 1998, Pages 135-138
Neuroscience Letters

Capsaicin facilitates excitatory but not inhibitory synaptic transmission in substantia gelatinosa of the rat spinal cord

https://doi.org/10.1016/S0304-3940(98)00730-7Get rights and content

Abstract

Actions of capsaicin were examined on synaptic transmissions in the substantia gelatinosa (SG) of adult rat spinal cord slices using the whole-cell patch-recording technique. Bath-applied capsaicin at a concentration of 2 μM activated a slow inward current (having an amplitude of 33 pA at −70 mV), which was accompanied by an increase in the frequency of glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs; by 234%); these actions were blocked by a capsaicin-receptor antagonist, capsazepine (10 μM). The capsaicin-induced increase in sEPSC frequency was resistant to tetrodotoxin (0.5–1 μM). On the other hand, capsaicin (2 μM) did not affect either glycine- or γ-aminobutyric acid-mediated spontaneous synaptic transmission. The results indicate that capsaicin enhances excitatory but not inhibitory synaptic transmission, possibly through a direct action on primary afferent terminals in the SG. As the SG has been thought to participate in nociceptive pathway, it is suggested that such a presynaptic action of capsaicin contributes to nociceptive transmissions.

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Acknowledgements

The present study was supported by the Human Frontier Science Program to M.Y. and Grants-in-Aid for Scientific Research to M.Y. and E.K. from the Ministry of Education, Science, Sports and Culture of Japan. K.Y. was supported partly by the National Natural Science Foundation of China.

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