Sodium currents in vagotomized primary afferent neurones of the rat
Article first published online: 5 AUG 2004
The Journal of Physiology
Volume 536, Issue 2, pages 445–458, October 2001
How to Cite
Lancaster, E. and Weinreich, D. (2001), Sodium currents in vagotomized primary afferent neurones of the rat. The Journal of Physiology, 536: 445–458. doi: 10.1111/j.1469-7793.2001.0445c.xd
- Issue published online: 5 AUG 2004
- Article first published online: 5 AUG 2004
- (Received 22 February 2001; accepted after revision 15 June 2001)
- 1Nodose ganglion neurones (NGNs) become less excitable following section of the vagus nerve. To determine the role of sodium currents (INa) in these changes, standard patch-clamp recording techniques were used to measure INa in rat NGNs maintained in vivo for 5–6 days following vagotomy, and then in vitro for 2–9 h.
- 2Total INa and INa density in vagotomized NGNs were similar to control values. However, steady-state INa inactivation in vagotomized NGNs was shifted −9 mV relative to control values (V11/2sol;2, −74 ± 2 vs.−65 ± 2 mV, P < 0.01) and INa activation was shifted by −7 mV (V11/2sol;2, −21 ± 2 vs.−14 ± 2 mV, P < 0.006). INa 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).
- 3The fraction of INa resistant to 1 μm tetrodotoxin (TTX-R) was halved in vagotomized NGNs (21 ± 8 vs. 56 ± 8 % of total INa, P < 0.05). This change from TTX-R INa to TTX-sensitive (TTX-S) INa may explain altered INa activation, inactivation and repriming in vagotomized NGNs.
- 4The contribution of alterations in INa to NGN firing patterns was assessed by measuring INa evoked by a series of action potential (AP) waveforms. In general, control NGNs produced large, repetitive TTX-R INa while vagotomized NGNs produced smaller TTX-S INa that rapidly inactivated during AP discharge. We conclude that TTX-R INa is important for sustained AP discharge in NGNs, and that its diminution underlies the decreased AP discharge of vagotomized NGNs.