Protons regulate the excitability properties of rat myelinated sensory axons in vitro through block of persistent sodium currents.
J Peripher Nerv Syst
; 17(1): 102-11, 2012 Mar.
Article
em En
| MEDLINE
| ID: mdl-22462671
ABSTRACT
Little information is available on the pH sensitivity of the excitability properties of mammalian axons. Computer-assisted threshold tracking in humans has helped to define clinically relevant changes of nerve excitability in response to hyperventilation and ischaemia, but in vivo studies cannot directly differentiate between the impact of pH and other secondary factors. In this investigation, we applied an excitability testing protocol to a rat saphenous skin nerve in vitro preparation. Changes in extracellular pH were induced by altering pCO(2) in the perfusate, and excitability properties of large myelinated fibres were measured in the pH range from 6.9 to 8.1. The main effect of protons on nerve excitability was a near linear increase in threshold which was accompanied by a decrease in strength-duration time constant reflecting mainly a decrease in persistent sodium current. In the recovery cycle, late subexcitability following 7 conditioning stimuli was substantially reduced at acid pH, indicating a block of slow but not of fast potassium channels. Changes in threshold electrotonus were complex, reflecting the combined effects of pH on multiple channel types. These results provide the first systematic data on pH sensitivity of mammalian nerve excitability properties, and may help in the interpretation of abnormal clinical excitability measurements.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Prótons
/
Células Receptoras Sensoriais
/
Axônios
/
Potenciais de Ação
/
Fibras Nervosas Mielinizadas
Tipo de estudo:
Guideline
Limite:
Animals
Idioma:
En
Revista:
J Peripher Nerv Syst
Assunto da revista:
NEUROLOGIA
Ano de publicação:
2012
Tipo de documento:
Article
País de afiliação:
Suíça