Cholinergic activation of the murine trachealis muscle via non-vesicular acetylcholine release involving low-affinity choline transporters.
In addition to quantal, vesicular release of acetylcholine (ACh), there is also non-quantal release at the motor endplate which is insufficient to evoke postsynaptic responses unless acetylcholinesterase (AChE) is inhibited. We here addressed potential non-quantal release in the mouse trachea by organ bath experiments and (immuno)histochemical methods. Electrical field stimulation (EFS) of nerve terminals elicited tracheal constriction that is largely due to ACh release. Classical enzyme histochemistry demonstrated acetylcholinesterase (AChE) activity in nerve fibers in the muscle and butyrylcholinesterase (BChE) activity in the smooth muscle cells. Acute inhibition of both esterases by eserine significantly raised tracheal tone which was fully sensitive to atropine. This effect was reduced, but not abolished, in AChE, but not in BChE gene-deficient mice. The eserine-induced increase in tracheal tone was unaffected by vesamicol (10(-5)M), an inhibitor of the vesicular acetylcholine transporter, and by corticosterone (10(-4)M), an inhibitor of organic cation transporters. Hemicholinium-3, in low concentrations an inhibitor of the high-affinity choline transporter-1 (CHT1), completely abrogated the eserine effects when applied in high concentrations (10(-4)M) pointing towards an involvement of low-affinity choline transporters. To evaluate the cellular sources of non-quantal ACh release in the trachea, expression of low-affinity choline transporter-like family (CTL1-5) was evaluated by RT-PCR analysis. Even though these transporters were largely abundant in the epithelium, denudation of airway epithelial cells had no effect on eserine-induced tracheal contraction, indicating a non-quantal release of ACh from non-epithelial sources in the airways. These data provide evidence for an epithelium-independent non-vesicular, non-quantal ACh release in the mouse trachea involving low-affinity choline transporters.
Institute for Anatomy and Cell Biology, Justus-Liebig-University, Universities of Giessen and Marburg Lung Center (UGMLC) and German Center for Lung Research (DZL), Excellence Cluster Cardio-Pulmonary System, 35385 Giessen, Germany. Electronic address: christina.nassenstein@anatomie.med.uni-giessen.de.
Christina
C
Nassenstein
Institute for Anatomy and Cell Biology, Justus-Liebig-University, Universities of Giessen and Marburg Lung Center (UGMLC) and German Center for Lung Research (DZL), Excellence Cluster Cardio-Pulmonary System, 35385 Giessen, Germany.
Silke
S
Wiegand
Laboratory for Experimental Trauma Surgery, Justus-Liebig University Giessen, 35392 Giessen, Germany.
Katrin S
KS
Lips
Department of Pharmacology, School of Pharmacy, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.
Guanfeng
G
Li
Department of Pharmacology, School of Pharmacy, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.
Jochen
J
Klein
Institute for Anatomy and Cell Biology, Justus-Liebig-University, Universities of Giessen and Marburg Lung Center (UGMLC) and German Center for Lung Research (DZL), Excellence Cluster Cardio-Pulmonary System, 35385 Giessen, Germany.
Wolfgang
W
Kummer
D000109:Acetylcholine / Q000378:metabolism*; D000110:Acetylcholinesterase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002091:Butyrylcholinesterase / Q000235:genetics / Q000378:metabolism; D004558:Electric Stimulation; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009045:Motor Endplate / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism*; D014132:Trachea / Q000033:anatomy & histology*
C488255:CHT1 protein, mouse; D026901:Membrane Transport Proteins; D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase; D000109:Acetylcholine
Acetylcholinesterase; Airway contraction; Butyrylcholinesterase; Choline transporter-like (CTL) family; High-affinity choline transporter (CHT1); Non-quantal acetylcholine