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

---

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.