著者

渡辺 リサ 北村 泰子 山田 仁三

出版者

日本疼痛学会

雑誌

PAIN RESEARCH (ISSN:09158588)

巻号頁・発行日

vol.18, no.3, pp.127-136, 2003

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Neurons in the reticular formation of the brainstem are thought to participate in transmission of nociceptive information. However, the role of the reticular formation for the pain mechanism remained to be disclosed. In the present study, extracellular single-unit activities were recorded from the nucleus reticularis magnocellularis and adjacent areas (RF) elicited by electrical, mechanical and thermal noxious stimuli of the rat sciatic nerve.<br>   Multiple-spikes responding to single electrical stimulation were recorded in the single neuron in RF, which responded to pinch. They were grouped into three types: 1) The latency of Fast type was not over 30 msec, although the intensity of electrical stimulation increased, 2) the latency of Slow type was over 200 msec, although the intensity was low, and 3) Mixed type had components of both Fast type and Slow type. Considering the latency and intensity, Fast type, Slow type and Mixed type received information carried via Aδ-fibers, C-fiber and Aδ- and C-fibers, respectively. In Fast type, Aδ-fibers terminated to the single neuron of lamina V, which axon terminated to the single neuron of RF.Since the diameter of Aδ-fibers was different,multiple spikes were obtained with the gradually increased intensity. In Slow type, the neuron of lamina I received C-fibers and sent information via the several interneurons in laminae III-IV to the neuron of lamina V, which axon terminated to the single neuron of RF. Since the diameter of C-fibers was different, multiple spikes were obtained with the gradually increased intensity. As the above-mentioned manner, in Mixed type, the neuron of lamina V received information from both Aδ- and C-fibers and projected to the single neuron of RF. Neurons with the spontaneous spikes had tendency to be reacted by pinch but not by thermal stimulation. Neurons without the spontaneous spikes were reacted by both pinch and thermal stimulation.<br>   It seems that the single neuron of RF receiving various information from the peripheral nerve activates the ascending reticular activating system and/or descending pain inhibitory system.

著者

渡辺 リサ 北村 泰子 山田 仁三

雑誌

Pain research : the journal of the Japanese Society for the Study of Pain = 日本疼痛学会誌 (ISSN:09158588)

巻号頁・発行日

vol.18, no.3, pp.127-136, 2003-09-30

参考文献数

33

著者

渡辺 リサ 北村 泰子 山田 仁三

出版者

日本疼痛学会

雑誌

Pain research : the journal of the Japanese Society for the Study of Pain = 日本疼痛学会誌 (ISSN:09158588)

巻号頁・発行日

vol.17, no.2, pp.75-84, 2002-07-31

参考文献数

21

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Neurons in the reticular formation (RF) of the brainstem are thought to participate in the transmission of nociceptive information, because they receive fibers of the spinothalamic tract. However, the role of RF for the pain mechanism remained to be studied. In the present study, extracellular single-unit activities were recorded from RF of the medulla oblongata elicited by mechanical and electrical noxious stimuli to either hind limb of anesthetized rats.<br>   Single-spike and multiple-spikes responding to single electrical stimulation were recorded in RF. Multiple-spikes were grouped into the following three types from the number of spikes and the latency of each spike. Type I had two to four spikes, and the latency of each spike was not constant. Type II had three to six spikes, and the latency of the first spike was constant. Type III had five to eight spikes, and the latency of each of first three spikes was constant.<br>   Noxious informations via Aδ- and C-fiber reached to laminae V-VIII and laminae I-II, respectively, of the spinal dorsal horn. Moreover, there were lamina V neurons projecting to lamina III-IV, and lamina III-IV neurons projecting to lamina I-II. The presence of three types suggests that informations from various cells of origin of spinoreticular tract converged on a single neuron of RF. Furthermore, the presence of three types suggests that repetitive electrical stimuli activate various-closed circuits between the RF regions, because each of the RF regions of midbrain, pons and medulla oblongata connected reciprocally. Considering that RF receives and projects ascending and descending fibers in the brain and the spinal cord and that RF has reciprocal connections among ipsilateral and contralateral regions, we assumed that multiple spikes of RF contribute continuously to facilitating pain perception.