| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2001: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2000: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Research Abstract |
It is well known that traumatic injury of trigeminal nerve sometimes follows a long time paresthesia and dysesthesia and we hypothesized that these symptoms might come from the long-term excitation of trigeminal nucleus. Therefore, using high-speed optical imaging technique, we observed the propagation of neuronal excitation in the nociceptive afferent transmission and modulating site the trigeminal subnucleus caudalis (Vc), which was evoked by stimulation of primary afferent fibers.
Medulla was removed from mice or rats, and coronal, sagittal or horizontal sectioned slices of 400 μm thicknesses were stained with a voltage-sensitive fluorescence dye RH414. Fluorescence and differential fluorescence images of a slice preparation were recorded using a high-speed imaging system. The tract of each slice was stimulated directly by single shock or a train of 30 pulses at 100 s^<-1>. Either in the sagittal or coronal slices, membrane excitation evoked by single stimulation of the tract did not expand in any directions. Larger propagations of evoked by the single stimulation to the marginal layer or substantia gelatinosa were observed in the sagittal rather than coronal slices. In contract, in the horizontal slices, propagations of membrane excitation, which were evoked by single stimulation, expanded from the Marginal layer (Mar) to the substantia gelatinosa (SG). And an exposure to CNQX suppressed these propagations. High frequency stimulation induced widely propagated and long-lasting membrane depolarizations within Mar, Mg and Magnocellularis area (Mar). Exposure to MK-801 suppressed the depolarization expansion to SG.
These results suggest that horizontal slice is suitable for the study on the excitation propagation evoked by the afferent fiber stimulation within the trigeminal caudalis. Moreover, these results also support that glutamate might also be a neurotransmitter within the trigeminal afferent pathway in Vc.
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