Presence and distribution of cholinergic nerves in rat mediastinal brown adipose tissue.
Brown adipose tissue (BAT) is richly provided with sympathetic noradrenergic nerves but is believed to lack a parasympathetic nerve supply. Acetylcholine is the predominant transmitter of postganglionic parasympathetic nerves. The vesicular acetylcholine transporter (VAChT) resides in synaptic vesicles of cholinergic nerve terminals and is used as a marker for peripheral cholinergic nerves. We sought cholinergic nerves in rat BAT using VAChT immunohistochemistry (IHC) on cryosections of interscapular, cervical, mediastinal, and perirenal depots. Mediastinal BAT was the sole depot provided with putative parasympathetic perivascular and parenchymal cholinergic nerves. The absence of vasoactive intestinal peptide-positive nerves suggested their nature as pure cholinergic fibers. By confocal microscopy, both cholinergic and noradrenergic nerves were detected in mediastinal BAT. Cold exposure and fasting led to increased density of VAChT-positive fibers and of noradrenergic sympathetic nerves at morphometry. The unexpected double innervation of mediastinal BAT may explain the inhibitory influence on thermogenesis observed after systemic injection of muscarinic antagonists in rats, and raises questions about the physiological role of its cholinergic nerve supply.
Giordano
Antonio
A
Institute of Normal Human Morphology, Faculty of Medicine, Via Tronto, 10/A, 60020 Ancona, Italy.
Frontini
Andrea
A
Castellucci
Mario
M
Cinti
Saverio
S
D000109:Acetylcholine / Q000378:metabolism*; D002001:Adipose Tissue, Brown / Q000294:innervation* / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D003080:Cold Temperature; D005215:Fasting; D007150:Immunohistochemistry; D008297:Male; D008482:Mediastinum; D026901:Membrane Transport Proteins; D018613:Microscopy, Confocal; D051381:Rats; D017207:Rats, Sprague-Dawley; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins / Q000378:metabolism*
D026901:Membrane Transport Proteins; C493461:Slc18a3 protein, rat; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins; D000109:Acetylcholine