Sodium channel inactivation kinetics of rat sensory and motor nerve fibres and their modulation by glutathione.
Na+ channel currents of rat motor and sensory nerve fibres were studied with the patch-clamp technique on enzymatically demyelinated axons. Differences between motor and sensory fibres in multi-channel inactivation kinetics and the gating of late single-channel currents were investigated. In the axon-attached mode, inactivation of multi-channel Na+ currents in sensory axons was best fitted with a single time constant while for motor axons two time constants were needed. Late single-channel currents in sensory axons were characterized by short openings whereas motor axons exhibited additional long single-channel openings. In contrast, in excised, inside-out membrane patches, no differences between motor and sensory fibres were found; in both types of fibre inactivation of multi-channel Na+ currents proceeded with two time constants and late single-channel currents showed short and long openings. After application of the reducing agent glutathione to the cytoplasmic side of excised inside-out patches, inactivation of Na+ currents in both motor and sensory fibres proceeded with a single, fast exponential time constant and late currents appeared with short openings only. These data indicate that the axonal metabolism may contribute to the different inactivation kinetics of Na+ current in motor and sensory nerve fibres.
Mitrović
N
N
Physiologisches Institut, Universität München, Germany.
Quasthoff
S
S
Grafe
P
P
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism; D005978:Glutathione / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D009046:Motor Neurons / Q000378:metabolism*; D009412:Nerve Fibers / Q000378:metabolism; D009475:Neurons, Afferent / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000187:drug effects* / Q000378:metabolism*
D015222:Sodium Channels; D005978:Glutathione