1993 Fiscal Year Final Research Report Summary
Studies on thalamic inhibitory mechanisms of nociception
| Project/Area Number |
04670071
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | Department of Physiology, Shiga University of Medical Sciennce |
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Principal Investigator |
YOKOTA Toshikatsu Department of Physiology, Shiga University of Medical Sciennce, Professor, 医学部, 教授 (10001752)
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| Co-Investigator(Kenkyū-buntansha) |
HIRATA Kazuhiko Department of Anesthesiology, Shiga University of Medical Sciennce, Accistant, 医学部, 助手 (30238357)
MINAMI Toshihede Department of Anesthesiology, Shiga University of Medical Sciennce, Accistant, 医学部, 助手 (60209830)
KOYAMA Natsu Department of Physiology, Shiga University of Medical Sciennce, Assistant, 医学部, 助手 (50135464)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Thalamus / Nucleus ventralis posterolateralis / Intralaminar nuclei / Analgesia / Ascending inhibition / Descending inhibition / Dorsal colunm simulation / Morphine |
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| Research Abstract |
In urethane-chloralose anesthetized cats, thalamic inhibitory mechanisms of nociception were studied. Single unit activities were recorded from the nucleus ventralis posterolateralis (VPL) ansd intralaminar nuclei, i.e., nucleus centralis lateralis (CL) and nucleus parafascicularis (Pf). 1. Conditioning electrical stimulation of the nucleus raphe magnus injibited responses of NS and WDR neurons in the VPL to test stimulation applied to both splanchnic nerve (SPL) and cervical ventrolateral funiclus (VLF). Thus, ascending inhibitory mechamisms acting upon NS and WDR neurons were revealed. 2. Conditioning stimulation applied to nucleus raphe dorsalis and/or mesencephalic periaqueductal gray inhibited responses of all the NS and WDR neurons tested in the VPL, while the same stimulation inhibited those of only 20 % of nociceptive neurons in the CL and Pf. The results indicate that the endogenous analgesic system arising from the NRD/PAG is primarity acting upon the lateral system of pain pathways includin the VPL.Nevertheless, in both the lateral and medial system, inhibitory mechanisms are operating at the level of the thalamus. 3. Conditioning electrical stimulation of the dorsal colum inhibited restonses of NS and VPL neurons to SPL and VLF stimulations in the VPL.Conditioning electrical stimulation of the somatosensory cortex also inhibited the same responses. An transcortical inhibitory mechanism and/or recurrent inhibitory mechanism acting upon NS and WDR neurons in the VPL were suggested. 4. Intravenous morphine suppressed responses of nociceptive neurons in both the VPL and intralaminar nuclei. It was suggested that the site of action of morphine is primarily the spinal dorsal horn in the lateral system, while it includens the thalamic nuclei in the medial system. 5. Intravenous alpha _2 agonists suppressed the reponses of NS and WDR reurons in the VPL to SPL stimulation, while had no effects on those to VLF stimulation.
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