Cervical spinal hemisection effects on spinal tissue oxygenation and long-term facilitation of phrenic, renal and splanchnic sympathetic nerve activity

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HYPOTHESES: Moderate acute intermittent hypoxia (mAIH) elicits plasticity in both respiratory (phrenic long-term facilitation; pLTF) and sympathetic nerve activity (sympLTF) in rats. Although mAIH produces pLTF in normal rats, inconsistent results are reported after cervical spinal cord injury (cSCI), possibly due to greater spinal tissue hypoxia below the injury site. There are no reports concerning cSCI effects on sympLTF. Since mAIH is being explored as a therapeutic modality to restore respiratory and non-respiratory movements in humans with chronic SCI, both effects are important. To understand cSCI effects on mAIH-induced pLTF and sympLTF, partial or complete C2 spinal hemisections (C2Hx) were performed and, 2 weeks later, we assessed: 1) ipsilateral cervical spinal tissue oxygen tension; 2) ipsilateral & contralateral pLTF; and 3) ipsilateral sympLTF in splanchnic and renal sympathetic nerves.

METHODS: Male Sprague-Dawley rats were studied intact, or after partial (single slice) or complete C2Hx (slice with ∼1 mm aspiration). Two weeks post-C2Hx, rats were anesthetized and prepared for recordings of bilateral phrenic nerve activity and spinal tissue oxygen pressure (PtO2). Splanchnic and renal sympathetic nerve activity was recorded in intact and complete C2Hx rats.

RESULTS: Spinal PtO2 near phrenic motor neurons was decreased after C2Hx, an effect most prominent with complete vs. partial injuries; baseline PtO2 was positively correlated with mean arterial pressure. Complete C2Hx impaired ipsilateral but not contralateral pLTF; with partial C2Hx, ipsilateral pLTF was unaffected. In intact rats, mAIH elicited splanchnic and renal sympLTF. Complete C2Hx had minimal impact on baseline ipsilateral splanchnic or renal sympathetic nerve activity and renal, but not splanchnic, sympLTF remained intact.

CONCLUSION: Greater tissue hypoxia likely impairs pLTF and splanchnic sympLTF post-C2Hx, although renal sympLTF remains intact. Increased sympathetic nerve activity post-mAIH may have therapeutic benefits in individuals living with chronic SCI since anticipated elevations in systemic blood pressure may mitigate hypotension characteristic of people living with SCI.

Medienart:

E-Artikel

Erscheinungsjahr:

2023

Erschienen:

2023

Enthalten in:

Zur Gesamtaufnahme - volume:368

Enthalten in:

Experimental neurology - 368(2023) vom: 15. Okt., Seite 114478

Sprache:

Englisch

Beteiligte Personen:

Perim, Raphael R [VerfasserIn]
Vinit, Stéphane [VerfasserIn]
Mitchell, Gordon S [VerfasserIn]

Links:

Volltext

Themen:

Acute intermittent hypoxia
Journal Article
Oxygen
Phrenic
Plasticity
Recovery
Research Support, N.I.H., Extramural
S88TT14065
Sympathetic activity

Anmerkungen:

Date Completed 08.09.2023

Date Revised 11.09.2023

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1016/j.expneurol.2023.114478

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM359523110