Electrophysiological mapping of the nociceptive inputs to the substantia gelatinosa in rat horizontal spinal cord slices

Go Kato, Hidemasa Furue, Toshihiko Katafuchi, Toshiharu Yasaka, Yukihide Iwamoto

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

To study the functional projection patterns of the primary afferents in the spinal cord, the postsynaptic responses of substantia gelatinosa (SG) neurones evoked by L5 dorsal root stimulation (DRS) were examined from the neurones located at L2 to S1 in horizontal slices of the adult rat spinal cord using a blind whole-cell patch-clamp technique. In the voltage-clamp mode, the L5 DRS evoked the Aδ and C-afferent-mediated excitatory postsynaptic currents (EPSCs) in more than 70% of the neurones tested at the L5 level. Both Aδ- and C-afferent EPSCs were also recorded in more than 50% of the neurones at L4. At L3 and L6, the number of neurones receiving the C-afferent EPSCs (> 40%) was significantly greater than that of Aδ-afferent EPSCs (< 20%). On the other hand, the Aδ and C-afferent-mediated inhibitory postsynaptic currents (IPSCs) elicited by L5 DRS were almost equally observed from L2 to S1. In the current-clamp mode, L5 DRS evoked Aδ and C-afferent-mediated EPSPs, some of which initiated action potentials (APs). Most of the Aδ-afferent-mediated APs were limited at the L5 level, while C-afferent-mediated APs were observed at L5 and L4. As the L2 DRS-evoked APs in the L2 SG neurones were suppressed by L5 DRS, the widespread distribution of the inhibitory inputs was considered to be functional. These findings suggest that the excitatory projection of the C afferents to the SG neurones was thus spread more rostrocaudally than that of the Aδ afferents, thereby contributing to more diffuse pain transmission. In addition, the widespread distribution of the inhibitory inputs may thus play a role as a lateral inhibitory network and thereby prevent the expansion of the excitatory inputs of noxious stimuli.

Original languageEnglish
Pages (from-to)303-315
Number of pages13
JournalJournal of Physiology
Volume560
Issue number1
DOIs
Publication statusPublished - Oct 1 2004

All Science Journal Classification (ASJC) codes

  • Physiology

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