1990 Fiscal Year Final Research Report Summary
Medullary Reticular Neurons Related to Hypoxic Respiratory Depression
| Project/Area Number |
01570424
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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 |
Respiratory organ internal medicine
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| Research Institution | University of Tsukuba |
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Principal Investigator |
ARITA Hideho Univ. of Tsukuba. Inst. Clin. Med. Sci., Assist. Prof., 基礎医学系, 講師 (20075576)
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| Project Period (FY) |
1989 – 1990
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| Keywords | hypoxic respiratory depression / serotonin / nucleus paragigantocellularis lateralis / control of breathing |
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| Research Abstract |
We have performed the following three distinct experiments.
1. Respiratory effect of intravertebral arterial injections of hypoxic or normoxic saline has been studied in sino-aortic denervated, vagotomized, artificially ventilated cats. Injections of N_2-saturated saline (a central hypoxic loading) evoked a clear respiratory depression (a decrease in phrenic nerve activity) with a short onset latency within a few seconds. Similar hypoxic respiratory depression was observed after decerebration at the mid-collicular level. Therefore, it was concluded that the structures responsible for the hypoxic respiratory depression were located within ponto-medullary regions supplied by the vertebral-basilar artery.
2. We have examined changes in activity of medullary reticular neurons with non-phasic discharges during the forementioned hypoxic respiratory depression. Both excitatory and inhibitory units were isolated, and most of them were found in the rostral vetrolateral medulla, corresponding to the nuleus paragigantocellularis lateralis.
3. Since it has been reported that brainstem serotonergic system was depressed during the central hypoxic loading, we have tested responsiveness of medullary inspiratory neurons to direct applications of serotonin, using a multi-barreled micropipette. The medullary inspiratory neurons examined herein were classified into two subgroups based upon the differences in firing patterns. The inspiratory neurons with decrementing firing pattern were excited by serotonin application, whereas the inspiratory neurons with augmenting firing pattern were inhibited. These results suggest a possibility that inspiratory premotor neurons supplying the dilator muscles of upper airway might be more sensitive to the hypoxic respiratory depression.
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