1994 Fiscal Year Final Research Report Summary
Roles of neural structures within the ventral medullary surface in the regulation of respiratory rhythm generation
| Project/Area Number |
05454138
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
General physiology
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| Research Institution | Chiba University |
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Principal Investigator |
FUKUDA Yasuichiro Chiba Univ., School of Medicine, Professor, 医学部, 教授 (10009649)
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| Co-Investigator(Kenkyū-buntansha) |
HAYASHI Fumiaki Chiba Univ., School of Medicine, Lecturer, 医学部, 講師 (80173029)
KAWAHARA Katumasa Chiba Univ., School of Medicine, Associate Professor, 医学部, 助教授 (70134525)
CHIBA Tanemichi Chiba Univ., School of Medicine, Professor, 医学部, 教授 (20009525)
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| Project Period (FY) |
1993 – 1994
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| Keywords | ventral medullary surface / respiratory rhythm / phrenic discharge / glossopharyngeal activity / pulmonary afferents / motoneuron distribution / rat |
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| Research Abstract |
Roles of ventral medullary surface structures in the generation and regulation of respiratory rhythmicity were examined in anesthetized rats. Inspiratory discharges of phrenic (Phr) and glossopharyngeal (stylopharyngeal muscle branch, IX) nerves were monitored during bilateral cooling of ventral medullary surface (VMS) at lateral border of pyramidal tract. In this VMS region, a cluster of neurons referred as Nucl. parapyramidal is superficialis was located in surface layr (<250mum). Phrenic nerve discharges disappeared while rhythmic IX activity remained during VMS cooling at 26-24ﾟC.The latter disappeared at 22-20ﾟC.Recovery of rhythmicity was noticed always first in the IX later in both nerves. It is therefore probable that the IX motoneurons are less suppressed than the Phr motoneurons by reduction in respiratory drive from VMS.Drive from VMS may play an essential role in the generation of rhythmicity.
Inspiratory inhibition by pulmonary stretch receptor activation by lung inflation was also less in the IX than in the Phr nerve discharges. This result also suggested that the IX motoneurons are less suppressed by inhibitory influence from slowly adapting pulmonary receptors.
Retrograde tracing of IX motoneurons by injection of HRP into stylopharyngeal muscle revealed that the cells were located at the site most rostral part of the Nucl.ambiguus closed to Botzinger complex or pre-Botzinger complex.
Above described results were obtained in exper imental condition with well oxygenated state of animals. Precise methods of measurement and maintenance of whole body oxygeneration were developed.
Further studies are required to elucidate functional and morphological relationship between VMS neurons and stylopharyngeal motoneurons or a rhythm generator neurons.
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