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Differential distribution of voltage gated K + ion channels in adult rat aortic baroreceptor neurons with myelinated and unmyelinated afferent fibers
Author(s) -
Li BaiYan,
Schild John Henry
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a775-a
Subject(s) - nodose ganglion , chemistry , baroreceptor , patch clamp , anatomy , nerve conduction velocity , biophysics , medicine , blood pressure , biology , heart rate , biochemistry , receptor , stimulation , vagus nerve
Voltage gated K + channels (K v ) are important in defining baroreceptor (BR) pressure‐discharge characteristics. We have shown that a Ca +2 ‐activated K + current (I K,Ca ) is expressed in aortic BR neurons (ABNs) with unmyelinated (UM) but not myelinated (M) fibers. Here, we quantify the expression of other K v subtypes in fluorescently identified ABNs using an intact nodose ganglion preparation for patch clamp study and measure of BR fiber conduction velocity. Voltage clamp recordings were performed using 450 msec steps (−70 to +40 mV, 5 mV increments) at an interval of 3 sec. The protocol was repeated but w/the addition of 10 nM α‐dendrotoxin, then again w/the addition of 5 mM 4‐AP and again with the addition of 15 mM TEA. Trace subtraction yielded the distribution of I DTX , I 4AP and I K currents. All ABNs with M‐fibers exhibited a whole cell K + current (I K,total ) magnitude (pA/pF) nearly twice that of neurons with UM‐fibers. The I K,total of ABNs with M‐fibers (n = 3) was comprised of (% total): 71.0 ± 6.1 I 4AP , 16.0 ± 2.7 I K , 10.0 ± 2.0 I DTX with a remnant of 7.0 ± 0.2. In stark contrast the I K,total of ABN with UM‐fibers (n = 11) was comprised of (% total) 48.1 ± 6.5 I 4AP , 20.3 ± 2.0 I K , 24.0 ± 3.5 I DTX with a remnant of 9.2 ± 2.7%. Analysis of the pooled data did not reveal any quantitative differences in the voltage‐ and time‐dependent properties of these K + currents, suggesting the expression of a common family of K v subtypes across M and UM baroreceptor afferents, although at markedly different levels of functional expression. These results demonstrate that ABNs with M‐fibers lack a functionally significant I K,Ca and that repolarization is dominated by I 4AP . Computational modeling results demonstrate how such an expression of K + ion channels leads to the uniquely different discharge patterns of M and UM baroreceptor afferents. NIH ‐ HL072012