Calcium modulates excitatory amino acid (EAA)- and substance P-induced rat dorsal horn cell responses.
- Author:
Hong Kee SHIN
1
;
Sok Han KANG
;
In Duk CHUNG
;
Kee Soon KIM
Author Information
1. Department of Physiology, School of Medicine, Hanyang University,Seoul, 133-791 South Korea.
- Publication Type:Original Article
- Keywords:
Dorsal horn neuron;
Excitatory amino acids;
Substance P;
Calcium channel antagonists;
Iontophoresis
- MeSH:
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
- From:The Korean Journal of Physiology and Pharmacology
1999;3(1):35-45
- CountryRepublic of Korea
- Language:English
-
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.
