| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1986: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
The present project has revealed the following new findings on dynamic properties and locations of the central chemoreceptors.
1. In order to stimulate repeatedly the central chemoreceptors, we developed a technique of vertebral arterial injections of CO2-saturated saline in decerebrated, spontaneously breathing cats. The injections evoked an initial transient inhibition of ongoing respiratory activity, followed by the subsequent excitation: the initial inhibition was due to activation of vascular nociceptors and the subsequent excitation due to stimulation of the central chemoreceptors (J. Appl. Physiol.).
2. Applying this technique, we studied the changes in activity of medullary neurons (146 units) with non-phasic discharges. Eighteen units were found to be excited exclusively by stimulation of the central chemoreceptors (namely, possible candidates for pH-sensitive neurons), and they were distributed mainly in the vicinity of ventral respiratory group (VRG) neurons as well as in the
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dorsal area ventral to the solitary tract (ST), though less in number (Brain Res. 1988).
3. Using liquid membrane pH microelectrodes, we found intramedullary regions in which ECF pH shifted to the acid side in the same time course as respiratory excitation when CO2 in the vertebral artery was raised in stepwise fashion. These areas were found to overlap with the regions of "possible candidates for pH-sensitive neurons"
4. The regions described above were revealed to be supplied by the following vessels (by means of Technovit); the anterior inferior cerebellar artery, the Posterior inferior cerebellar artery and an unnamed artery arising from the basilar artery.
Based upon the foregoing evidence, we have hypothesized that the central chemoreceptors would consist of pH-sensitive neurons and the surrounding structures (capillaries and glial cells) which regulate ECF pH, and that they are located in the vicinity of the VRG and in the dorsal area ventral to the ST, which were perfused by the vertebral basilar arterial system. Less
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