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
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.