title: Expression of nicotinic acetylcholine receptor subunit mRNA in mouse bladder afferent neurons.
abstract: Nicotinic acetylcholine receptors (nAChR) influence bladder afferent activity and reflex sensitivity, and have been suggested as potential targets for treating detrusor overactivity. Mechanisms may include indirect effects, e.g. involving the urothelium, and direct action on nAChR expressed by afferent neurons. Here we determined the nAChR repertoire of bladder afferent neurons by retrograde neuronal tracing and laser-assisted microdissection/reverse transcriptase polymerase chain reaction (RT-PCR), and quantified retrogradely labelled nAChRα3-subunit-expressing neurons by immunohistochemistry in nAChR α3β4α5 cluster enhanced green fluorescent protein (eGFP) reporter mice. Bladder afferents distinctly expressed mRNAs encoding for nAChR-subunits α3, α6, α7, β2-4, and weakly α4. Based upon known combinatorial patterns of subunits, this predicts the expression of at least three basically different subunits of nAChR - α3(∗), α6(∗) and α7(∗) - and of additional combinations with β-subunits and α5. Bladder afferents were of all sizes, and their majority (69%; n=1367) were eGFP-nAChRα3 positive. Immunofluorescence revealed immunoreactivities to neurofilament 68 (NF68), transient receptor potential cation channel vanilloid 1 (TRPV1), substance P (SP) and calcitonin gene-related peptide (CGRP) in eGFP-nAChRα3-positive and -negative neurons. For each antigen, all possible combinations of colocalisation with eGFP-nAChRα3 were observed, with eGFP-nAChRα3-positive bladder neurons without additional immunoreactivity being most numerous, followed by triple-labelled neurons. In conclusion, more than one population of bladder afferent neurons expresses nAChR, indicating that peripheral nicotinic initiation and modulation of bladder reflexes might result, in addition to indirect effects, from the direct activation of sensory terminals. The expression of multiple nAChR subunits offers the potential of selectively addressing functional aspects and/or sensory neuron subpopulations.
authors.affiliation: Institute for Anatomy and Cell Biology, Justus-Liebig-University, Giessen, Germany, Aulweg 123, 35392 Giessen, Germany. rajender.nandigama@anatomie.med.uni-giessen.de
authors.forename: R
authors.initials: R
authors.lastname: Nandigama
authors.forename: I
authors.initials: I
authors.lastname: Ibañez-Tallon
authors.forename: K S
authors.initials: KS
authors.lastname: Lips
authors.forename: U
authors.initials: U
authors.lastname: Schwantes
authors.forename: W
authors.initials: W
authors.lastname: Kummer
authors.forename: T
authors.initials: T
authors.lastname: Bschleipfer
mesh_terms: D000818:Animals; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D056325:Neuronal Tract-Tracers; D009475:Neurons, Afferent / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000235:genetics* / Q000378:metabolism; D001743:Urinary Bladder / Q000294:innervation* / Q000378:metabolism
chemical_list: D056325:Neuronal Tract-Tracers; D012333:RNA, Messenger; D011978:Receptors, Nicotinic