1993 Fiscal Year Final Research Report Summary
Effects of conditioning stimulation of amygdaloid nucleus on tooth pulp driven-neurons in first somatosensory cortex (SI) of the cat
| Project/Area Number |
03670871
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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 |
Functional basic dentistry
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| Research Institution | Iwate Medical University |
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Principal Investigator |
KAWARADA Kei Iwate Medical University School of Dentistory Research Associate, 歯学部, 助手 (90204792)
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| Project Period (FY) |
1991 – 1993
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| Keywords | Limbic system / Periamygdaloid cortex / Amygdaloid complex / Condisioning Stimulation / Tooth pulp driven neuron / Somatosensory cortex / Nociception / Analgesia |
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| Research Abstract |
(1) To demonstrate that the amygdaloid complex modulate the nociception, we observed the effect of amygdaloid conditioning stimulation on the jaw-opening reflex(JOR) regarded as a nociceptive reflex in the cat. The stimulation of the central nucleus(ACE) inhibited the JOR induced by the electrical stimulation of tooth pulp, but the other amygdaloid nuclei did not influence on the reflex. Additionally, further experiments suggested that the JOR inhibitory effect on ACE acts on the trigeminal motor nucleus rather than the sensory nuclei.
(2) We investigated the cat brain sites that were excited by the electrical stimulation of tooth pulp using c-fos immunoreactivity. The number of Fos-positive cells in the tooth pulp-stimulated group increased in the ipsilateral trigeminal caudal nucleus and parabrachial nucleus, and the bilateral lateral habenular nucleus and supraoptic nucleus compared with the anesthetic- or saline- injected groups. The increaes were inhibited by morphine pretreatment.
(3) To elucidate the amygdaloid complex and the surrounding areas have any role in nociception, we studied the effect of conditioning stimulation of these areas on the tooth pulp-driven (TPD) neurons in the first somatosensory cortex of the cat. The stimulation of the amygdaloid nuclei did not alter the activities of TPD neurons as indicated in the result 1. On the other hand, the conditioning stimulation of the periamygdaloid cortex(PAM) located in the ventral side of amygdaloid complex markedly suppressed the slow responses of TPD neurons. Furthermore, this inhibitory effect was antagonized by naloxone.
Results 1 and 3 suggest that the amygdaloid complex and the surrounding area(PAM) decrease the reactions to noxious stimulation by means of the inhibition of both sensory and motor systems.
(4) To investigate the inhibitory sites observed in result 3, we are planing the further studies by the c-fos expression as indicated in result 2.
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