POTASSIUM CURRENTS OF NEURONS ISOLATED FROM MEDIAL NUCLEUS-TRACTUS-SOLITARIUS

Authors
Citation
Jp. Moak et Dl. Kunze, POTASSIUM CURRENTS OF NEURONS ISOLATED FROM MEDIAL NUCLEUS-TRACTUS-SOLITARIUS, The American journal of physiology, 265(5), 1993, pp. 80001596-80001602
Citations number
19
Categorie Soggetti
Physiology
ISSN journal
00029513
Volume
265
Issue
5
Year of publication
1993
Part
2
Pages
80001596 - 80001602
Database
ISI
SICI code
0002-9513(1993)265:5<80001596:PCONIF>2.0.ZU;2-H
Abstract
Voltage-dependent potassium currents of neurons enzymatically isolated from the medial and dorsal subnuclei of the solitary tract (mNTS) of adult guinea pig have been characterized with respect to their voltage dependence, time dependence, and sensitivity to specific blocking age nts. This region of the medulla receives baroreceptor afferent input a nd is involved in cardiovascular regulation. Our results showed the pr esence of three types of potassium currents. First, in all neurons stu died (n = 58) a slowly developing outward current was present at poten tials more positive than -30 mV. The time to half-peak current decreas ed with depolarization [24.8 ms at 0 mV; 19.2 ms at +10 mV; 12.5 ms at +20 mV; 9.9 ms at +30 mV (n = 4)]. This current required 20 mM tetrae thylammonium (TEA) for full block and failed to show significant inact ivation for voltage commands up to 300 ms. Second, a rapidly activatin g, 4-aminopyridine (4-AP)-sensitive transient outward potassium curren t was present in 83% of the cells examined (n = 39/47). Threshold for activation was -30 mV. The current relaxation consisted of three compo nents: tau1 = 14-49 ms; tau2 = 174-362; tau3 = 1.1-2.4 s. Finally, in all cells tested calcium activated a large nontransient outward potass ium current that was inhibited by charybdotoxin. The studies reported here will be used in conjunction with studies describing sodium and ca lcium currents to understand the basis for generation of activity in t he mNTS in response to baroreceptor input.