title: Sodium currents in vagotomized primary afferent neurones of the rat.
abstract: 1. Nodose ganglion neurones (NGNs) become less excitable following section of the vagus nerve. To determine the role of sodium currents (I(Na)) in these changes, standard patch-clamp recording techniques were used to measure I(Na) in rat NGNs maintained in vivo for 5-6 days following vagotomy, and then in vitro for 2-9 h. 2. Total I(Na) and I(Na) density in vagotomized NGNs were similar to control values. However, steady-state I(Na) inactivation in vagotomized NGNs was shifted -9 mV relative to control values (V(1/2), -74 +/- 2 vs. -65 +/- 2 mV, P < 0.01) and I(Na) activation was shifted by -7 mV (V(1/2), -21 +/- 2 vs. -14 +/- 2 mV, P < 0.006). I(Na) recovery from inactivation was also slower in vagotomized NGNs (fast time constant, 2.8 +/- 0.4 vs. 1.6 +/- 0.3 ms, P < 0.02). 3. The fraction of I(Na) resistant to 1 microM tetrodotoxin (TTX-R) was halved in vagotomized NGNs (21 +/- 8 vs. 56 +/- 8 % of total I(Na), P < 0.05). This change from TTX-R I(Na) to TTX-sensitive (TTX-S) I(Na) may explain altered I(Na) activation, inactivation and repriming in vagotomized NGNs. 4. The contribution of alterations in I(Na) to NGN firing patterns was assessed by measuring I(Na) evoked by a series of action potential (AP) waveforms. In general, control NGNs produced large, repetitive TTX-R I(Na) while vagotomized NGNs produced smaller TTX-S I(Na) that rapidly inactivated during AP discharge. We conclude that TTX-R I(Na) is important for sustained AP discharge in NGNs, and that its diminution underlies the decreased AP discharge of vagotomized NGNs.
authors.affiliation: The Neuroscience Program, University of Maryland, School of Medicine, 655 West Baltimore Street, Baltimore, MD 21201-1559, USA.
authors.forename: E
authors.initials: E
authors.lastname: Lancaster
authors.forename: D
authors.initials: D
authors.lastname: Weinreich
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008297:Male; D009475:Neurons, Afferent / Q000378:metabolism*; D009620:Nodose Ganglion / Q000166:cytology* / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014628:Vagotomy
chemical_list: D000779:Anesthetics, Local; D015222:Sodium Channels; D013779:Tetrodotoxin; D012964:Sodium