Effects of calcium channel blocker on the response properties of spinal dorsal horn neurons

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08671736
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Anesthesiology/Resuscitation studies
• Research Institution: Shimane Medical University
• Principal Investigator: YAMAMORI Yuji Shimane Medical University, Intensive Care Unit, Assistant Professor, 医学部, 講師 (80230598)
• Co-Investigator(Kenkyū-buntansha): UCHIDA Hiroshi Shimane Medical University, Anesthesiology, Assistant Professor, 医学部, 講師 (70176692) ; SAITO Yoji Shimane Medical University, Anesthesiology, Associate Professor, 医学部, 助教授 (50162243)
• Project Period (FY): 1996 – 1997
• Keywords: Spinal neuron / Receptive field / Calcium channel blocker

Research Abstract

Calcium ion may play an important role on sensory transmission of neurons. The change of calcium current in sensory neurons may be one mechanism of pain. The purpose of this study was to examine (1) the effects of calcium channel blocker, diltiazem on spinal dorsal horn neuronal responses and (2) the effects of calcium channel blocker, diltiazem on PGF_<2alpha> -induced increases of spinal dorsal horn neuronal responses.
Extracellular activity of single spinal dorsal horn neurons were recorded in decerebrated rats. The size of low-threshold RF and responses to brushing were determined. (1) Following determination of control RF size and resopnses to brushing, each profile was again evaluated after administration of diltiazem (500mug/10l) from intrathecal catheter. (2) Following determination of PGF_<2alpha>-induced changes of each neuron's profiles, each profile was again evaluated after administration of diltiazem (500mug/10l) from intrathecal catheter.
(1) Four neurons have been studied. All neurons were low threshold (LT) neurons. The mean RF size was decreased by 75%, 75% and 35% from the baseline level at 10,20 and 30 minutes after diltiazemrespectively. The responses to brushing ahd the same tendency as RF.(2) Seven neurons (6 LT neurons and 1 WDR neuron) have been studied. Four neurons out of five showed increase of RF,and one neuron showed no change after PGF_<2alpha>. While intrathecally administered saline induced no change of RF in two neurons. The mean RF size was increased by 33%, 57% and 66% from the baseline level at 10,30 and 60 minutes after PGF_<2alpha>, respectively. The PGF_<2alpha>-induced increase of the RF size was reduced by 91%, 83% and 53% at 10,20 and 30 minuts after the administration of diltiazem.
There results suggest that (1) calcium channel blocker, diltiazem induces decrease of spinal dorsal horn neuronal responses, (2) hypersensitive state produced by PGs in the spinal level is reversed by calcium channel blocker.