Low-level vagus nerve stimulation upregulates small conductance calcium-activated potassium channels in the stellate ganglion.
BACKGROUND
Small conductance calcium-activated potassium (SK) channels are responsible for afterhyperpolarization that suppresses nerve discharges.


OBJECTIVE
To test the hypothesis that low-level vagus nerve stimulation (LL-VNS) leads to the upregulation of SK2 proteins in the left stellate ganglion.


METHODS
Six dogs (group 1) underwent 1-week LL-VNS of the left cervical vagus nerve. Five normal dogs (group 2) were used as controls. SK2 protein levels were examined by using Western blotting. The ratio between SK2 and glyceraldehydes-3-phosphate-dehydrogenase levels was used as an arbitrary unit (AU).


RESULTS
We found higher SK2 expression in group 1 (0.124 ± 0.049 AU) than in group 2 (0.085 ± 0.031 AU; P<.05). Immunostaining showed that the density of nerve structures stained with SK2 antibody was also higher in group 1 (11,546 ± 7,271 μm(2)/mm(2)) than in group 2 (5321 ± 3164 μm(2)/mm(2); P<.05). There were significantly more ganglion cells without immunoreactivity to tyrosine hydroxylase (TH) in group 1 (11.4%±2.3%) than in group 2 (4.9% ± 0.7%; P<.05). The TH-negative ganglion cells mostly stained positive for choline acetyltransferase (95.9% ± 2.8% in group 1 and 86.1% ± 4.4% in group 2; P = .10). Immunofluorescence confocal microscopy revealed a significant decrease in the SK2 staining in the cytosol but an increase in the SK2 staining on the membrane of the ganglion cells in group 1 compared to group 2.


CONCLUSIONS
Left LL-VNS results in the upregulation of SK2 proteins, increased SK2 protein expression in the cell membrane, and increased TH-negative (mostly choline acetyltransferase-positive) ganglion cells in the left stellate ganglion. These changes may underlie the antiarrhythmic efficacy of LL-VNS in ambulatory dogs.
Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
Mark J
MJ
Shen
Hao-Che Chang
Hyung-Wook
HW
Park
A
A
George Akingba
Po-Cheng
PC
Chang
Zheng Zhang
Shien-Fong
SF
Lin
Changyu
C
Shen
Lan S
LS
Chen
Zhenhui
Z
Chen
Michael C
MC
Fishbein
Nipavan
N
Chiamvimonvat
Peng-Sheng
PS
Chen
D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000502:physiology; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D004285:Dogs; D004567:Electrodes, Implanted; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D013233:Stellate Ganglion / Q000502:physiology*; D015854:Up-Regulation / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology; D055536:Vagus Nerve Stimulation
D051640:Small-Conductance Calcium-Activated Potassium Channels; D002795:Choline O-Acetyltransferase