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Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_11 | Pages 300 - 300
1 Jul 2014
Miyakawa T Takebayashi T Terasima Y Ohgon I Yamashita T
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Summary Statement

TRPA1 antagonist reduced spontaneous excitatory postsynaptic currents of substantia gelatinosa neuron in spinal cord dorsal horn by in vivo patch-clamp analysis. TRPA1 may act as a mediator of excitatory synaptic transmission.

Introduction

Little is known about the pathophysiological mechanisms of radicular pain. The substantia gelatinosa (SG) in the spinal cord dorsal horn receives primary afferent inputs, which predominantly convey nociceptive sensations. Nociceptive information is modified and integrated in the SG, suggesting that the SG may be a therapeutic target for treating radicular pain. Electrophysiological study using in vivo patch-clamp recording from SG neurons is a useful method to analyze functional properties in synaptic transmission. Transient receptor potential ankyrin 1 (TRPA1) has been widely identified in the central and peripheral nervous system such as peripheral nociceptor, dorsal root ganglion (DRG), and spinal cord dorsal horn, and is considered that they are involved in synaptic transmission of pain. However, it is still unknown about its functional role and mechanism of pain transmission in spinal cord dorsal horn. The purpose of this study is to investigate changes in excitatory synaptic transmission of SG neurons with TRPA1 antagonist and to clarify the potential role of TRPA1 in the rat spinal cord dorsal horn using in vivo patch-clamp analysis.


Bone & Joint Research
Vol. 1, Issue 9 | Pages 198 - 204
1 Sep 2012
Iwase T Takebayashi T Tanimoto K Terashima Y Miyakawa T Kobayashi T Tohse N Yamashita T

Objectives

In order to elucidate the influence of sympathetic nerves on lumbar radiculopathy, we investigated whether sympathectomy attenuated pain behaviour and altered the electrical properties of the dorsal root ganglion (DRG) neurons in a rat model of lumbar root constriction.

Methods

Sprague-Dawley rats were divided into three experimental groups. In the root constriction group, the left L5 spinal nerve root was ligated proximal to the DRG as a lumbar radiculopathy model. In the root constriction + sympathectomy group, sympathectomy was performed after the root constriction procedure. In the control group, no procedures were performed. In order to evaluate the pain relief effect of sympathectomy, behavioural analysis using mechanical and thermal stimulation was performed. In order to evaluate the excitability of the DRG neurons, we recorded action potentials of the isolated single DRG neuron by the whole-cell patch-clamp method.


The Journal of Bone & Joint Surgery British Volume
Vol. 89-B, Issue 12 | Pages 1666 - 1672
1 Dec 2007
Mizuno S Takebayashi T Kirita T Tanimoto K Tohse N Yamashita T

A rat model of lumbar root constriction with an additional sympathectomy in some animals was used to assess whether the sympathetic nerves influenced radicular pain. Behavioural tests were undertaken before and after the operation.

On the 28th post-operative day, both dorsal root ganglia and the spinal roots of L4 and L5 were removed, frozen and sectioned on a cryostat (8 μm to 10 μm). Immunostaining was then performed with antibodies to tyrosine hydroxylase (TH) according to the Avidin Biotin Complex method. In order to quantify the presence of sympathetic nerve fibres, we counted TH-immunoreactive fibres in the dorsal root ganglia using a light microscope equipped with a micrometer graticule (10 x 10 squares, 500 mm x 500 mm). We counted the squares of the graticule which contained TH-immunoreactive fibres for each of five randomly-selected sections of the dorsal root ganglia.

The root constriction group showed mechanical allodynia and thermal hyperalgesia. In this group, TH-immunoreactive fibres were abundant in the ipsilateral dorsal root ganglia at L5 and L4 compared with the opposite side. In the sympathectomy group, mechanical hypersensitivity was attenuated significantly.

We consider that the sympathetic nervous system plays an important role in the generation of radicular pain.


The Journal of Bone & Joint Surgery British Volume
Vol. 88-B, Issue 4 | Pages 554 - 557
1 Apr 2006
Takebayashi T Cavanaugh JM Kallakuri S Chen C Yamashita T

To clarify the pathomechanisms of discogenic low back pain, the sympathetic afferent discharge originating from the L5-L6 disc via the L2 root were investigated neurophysiologically in 31 Lewis rats. Sympathetic afferent units were recorded from the L2 root connected to the lumbar sympathetic trunk by rami communicantes. The L5-L6 discs were mechanically probed, stimulated electrically to evoke action potentials and, finally, treated with chemicals to produce an inflammatory reaction. We could not obtain a response from any units in the L5-L6 discs using mechanical stimulation, but with electrical stimulation we identified 42 units consisting mostly of A-delta fibres. In some experiments a response to mechanical probing of the L5-L6 disc was recognised after producing an inflammatory reaction. This study suggests that mechanical stimulation of the lumbar discs may not always produce pain, whereas inflammatory changes may cause the disc to become sensitive to mechanical stimuli, resulting in nociceptive information being transmitted as discogenic low back pain to the spinal cord through the lumbar sympathetic trunk. This may partly explain the variation in human symptoms of degenerate discs.


The Journal of Bone & Joint Surgery British Volume
Vol. 79-B, Issue 3 | Pages 490 - 493
1 May 1997
Takebayashi T Yamashita T Minaki Y Ishii S

We have studied the mechanosensitive afferent units in the lateral ligament of the ankle of the cat, with reference to the causes of lateral instability after injury, using electrophysiological recording from the lumbar dorsal rootlets.

We identified 30 mechanosensitive units in the lateral ligament; 28 (93%) were located near the attachment to the fibula and calcaneus, which included both low-threshold group-II units and low- and high-threshold group-III units. Our results indicate that there are both proprioceptors and nociceptors in the lateral ligament of the cat ankle, and confirm that afferent fibres from the lateral ligament may contribute to the stability of the joint by regulation of position and movement.