Galanin is localized in sympathetic neurons of the dog liver.
Mundinger, Thomas O., C. Bruce Verchere, Denis G. Baskin, Michael R.
Boyle, Stephan Kowalyk, and Gerald J. Taborsky, Jr.
Department of Medicine and Department of Biological Structure,
University of Washington, Seattle WA 98195, Division of Endocrinology
and Metabolism, Veterans Affairs Puget Sound Health Care System,
Seattle, WA 98108
APStracts 4:0186E, 1997.
Stimulation of canine hepatic nerves releases the neuropeptide galanin
from the liver, therefore galanin may be a sympathetic
neurotransmitter in the dog liver. To test this hypothesis, we used
immunocytochemistry to determine if galanin is localized in hepatic
sympathetic nerves, and we used hepatic sympathetic denervation to
verify such localization. Liver sections from dogs were immunostained
for both galanin and the sympathetic enzyme marker, tyrosine
hydroxylase (TH). Galanin-like immunoreactivity (GALIR) was
colocalized with TH in many axons of nerve trunks as well as
individual nerve fibres located both in the stroma of hepatic blood
vessels and in the liver parenchyma. Neither galanin-positive nor TH
-positive cell bodies were observed. Intraportal 6-hydroxy-dopamine
(6-OHDA) infusion, a treatment which selectively destroys hepatic
adrenergic nerve terminals, abolished the GALIR staining in
parenchymal neurons but only moderately diminished the GALIR staining
in the nerve fibres around blood vessels. To confirm that 6-OHDA
pretreatment proportionally depleted galanin and norepinephrine in
the liver, we measured both the liver content of and the hepatic
nerve-stimulated spillover of galanin and norepinephrine from the
liver. Pretreatment with 6-OHDA reduced the content and spillover of
both galanin and norepinephrine by more than 90%. Together these
results indicate that galanin in dog liver is primarily colocalized
with norepinephrine in sympathetic nerves and may therefore function
as a hepatic sympathetic neurotransmitter.
Received 12 May 1997; accepted in final form 14 August 1997.
APS Manuscript Number E215-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 27 August 1997