Heterogeneity of neuromuscular junctions in striated muscle of human esophagus demonstrated by triple staining for the vesicular acetylcholine transporter, alpha-bungarotoxin, and acetylcholinesterase.
During studies on enteric co-innervation in the human esophagus, we found that not all acetylcholinesterase (AChE)-positive motor endplates stained for alpha-bungarotoxin (alpha-BT) and the vesicular acetylcholine transporter (VAChT), respectively. Therefore, we probed for differences in neuromuscular junctions in human esophagus by using triple staining for VAChT, alpha-BT, and AChE followed by qualitative and quantitative analysis. To exclude that the results were caused by processing artifacts, we additionally examined the influence of a number of factors including post-mortem changes and the type and duration of fixation on the staining results. Four types of neuromuscular junction could be distinguished in human esophagus: type I with VAChT-positive and type II with VAChT-negative nerve terminals on a alpha-BT-positive and AChE-positive endplate area, type III with VAChT-positive nerve terminals on a alpha-BT-negative but AChE-positive endplate area, and type IV with VAChT-negative nerve terminals on a alpha-BT-negative but AChE-positive endplate area. On average, 32% of evaluated AChE-positive motor endplates were type I, 6% type II, 24% type III, and 38% type IV. Based on these results, we suggest that, in human esophagus, (1) the most reliable method for staining motor endplates is presently AChE histochemistry, (2) alpha-BT-sensitive and alpha-BT-resistant nicotinic acetylcholine receptors exist in neuromuscular junctions, and (3) different types of VAChT or transport mechanisms for acetylcholine probably exist in neuromuscular junctions.
Kallmünzer
Bernd
B
Institute of Anatomy, University of Erlangen-Nuremberg, Krankenhausstrasse 9, 91054, Erlangen, Germany.
Sörensen
Björn
B
Neuhuber
Winfried L
WL
Wörl
Jürgen
J
D000110:Acetylcholinesterase / Q000378:metabolism*; D000368:Aged; D002038:Bungarotoxins / Q000378:metabolism*; D004947:Esophagus / Q000294:innervation* / Q000378:metabolism*; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009045:Motor Endplate / Q000378:metabolism; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000378:metabolism; D050494:Vesicular Acetylcholine Transport Proteins / Q000378:metabolism*
D002038:Bungarotoxins; D011978:Receptors, Nicotinic; C493459:SLC18A3 protein, human; D050494:Vesicular Acetylcholine Transport Proteins; D000110:Acetylcholinesterase