Korean J Physiol Pharmacol.  1999 Feb;3(1):35-45.

Calcium modulates excitatory amino acid (EAA)- and substance P-induced rat dorsal horn cell responses

• Shin HK
• Kang SH
• Chung ID
• Kim KS

Abstract

Excitatory amino acid (EAA) and substance P (SP) have been known to be primary candidates for nociceptive neurotransmitter in the spinal cord, and calcium ions are implicated in processing of the sensory informations mediated by EAA and SP in the spinal cord. In this study, we examined how Ca2+ modified the responses of dorsal horn neurons to single or combined iontophoretical application of EAA and SP in the rat. All the LT cells tested responded to kainate, whereas about 55% of low threshold (LT) cells responded to iontophoretically applied NMDA. NMDA and kainate excited almost all wide dynamic range (WDR) cells. These NMDA- and kainate-induced WDR cell responses were augmented by iontophoretically applied EGTA, but suppressed by Ca2+, Mn2+ verapamil and omega-conotoxin GVTA, effect of verapamil being more prominent and well sustained. Ca2+ and Mn2+ antagonized the augmenting effect of EGTA. On the other hand, prolonged spinal application of EGTA suppressed the response of WDR cell to NMDA. SP had triple effects on the spontaneous activity as well as NMDA-induced responses of WDR cells: excitation, inhibition and no change. EGTA augmented, but Ca2+, Mn2+ and verapamil suppressed the increase in the NMDA-induced responses and spontaneous activities of WDR cells following iontophoretical application of SP. These results suggest that in the spinal cord, sensory informations mediated by single or combined action of EAA and SP can be modified by the change in calcium ion concentration.

Keyword

Dorsal horn neuron; Excitatory amino acids; Substance P; Calcium channel antagonists; Iontophoresis

MeSH Terms

Animals
Calcium*
Egtazic Acid
Excitatory Amino Acids*
Hand
Ions
Iontophoresis
Kainic Acid
N-Methylaspartate
Neurotransmitter Agents
omega-Conotoxins
Posterior Horn Cells*
Rats*
Spinal Cord
Substance P
Verapamil
Calcium
Egtazic Acid
Excitatory Amino Acids
Ions
Kainic Acid
N-Methylaspartate
Neurotransmitter Agents
Substance P
Verapamil
omega-Conotoxins