Application of near infra-red laser light increases current threshold in optic nerve consistent with increased Na+-dependent transport.
Pflugers Arch
; 476(5): 847-859, 2024 May.
Article
em En
| MEDLINE
| ID: mdl-38421407
ABSTRACT
Increases in the current threshold occur in optic nerve axons with the application of infra-red laser light, whose mechanism is only partly understood. In isolated rat optic nerve, laser light was applied near the site of electrical stimulation, via a flexible fibre optic. Paired applications of light produced increases in threshold that were reduced on the second application, the response recovering with increasing delays, with a time constant of 24 s. 3-min duration single applications of laser light gave rise to a rapid increase in threshold followed by a fade, whose time-constant was between 40 and 50 s. After-effects were sometimes apparent following the light application, where the resting threshold was reduced. The increase in threshold was partially blocked by 38.6 mM Li+ in combination with 5 µ M bumetanide, a manoeuvre increasing refractoriness and consistent with axonal depolarization. Assessing the effect of laser light on the nerve input resistance ruled out a previously suggested fall in myelin resistance as contributing to threshold changes. These data appear consistent with an axonal membrane potential that partly relies on temperature-dependent electroneutral Na+ influx, and where fade in the response to the laser may be caused by a gradually diminishing Na+ pump-induced hyperpolarization, in response to falling intracellular [Na+].
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Nervo Óptico
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Sódio
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Axônios
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Lasers
Limite:
Animals
Idioma:
En
Revista:
Pflugers Arch
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Reino Unido