Wolff_2012_Life.Sci_91_1003

AIMS: In the oviduct, muscarinic acetylcholine receptors (MR) are linked with motility regulation and nicotinic receptors (nAChR) with ectopic pregnancy. We here aimed to determine the repertoire of cholinergic receptor expression in the murine oviduct and their functional coupling to regulation of intracellular calcium concentration ([Ca(2+)](i)). MAIN
METHODS: Cholinergic receptor transcripts were assessed by RT-PCR in oviductal segments (ampulla, isthmus, uterotubar junction) in all cyclic stages and pregnancy, and in laser-microdissected samples of epithelium and smooth muscle, nAChR subunit alpha3 distribution in tissue sections using an appropriate genetic reporter mouse strain. [Ca(2+)](i) responses were monitored in ciliated and non-ciliated oviductal cells isolated from wild-type and MR subtypes 1 and 3 gene deficient mice. KEY FINDINGS: Transcripts for all MR subtypes (M1-M5) are constantly expressed whereas there is some variability in nAChR expression from individual to individual. The qualitative expression pattern is independent from the hormonal status of the animal, except for nAChR alpha7, which is less present during pregnancy. The epithelium expresses M1, M3, nAChR alpha7 (data from laser-assisted microdissection) and nAChR alpha3 (ultrastructural investigation of reporter mice). MR dominate over nAChR in increasing [Ca(2+)](i) with being M3 the major, but not sole subtype driving this effect. The general nAChR inhibitor mecamylamine enhances muscarinic and purinergic responses. SIGNIFICANCE: In conclusion, the murine oviduct is endowed with a multiplicity of muscarinic and nicotinic receptors subtypes that, with respect to regulation of [Ca(2+)](i), are inversely linked to each other. The major, but not sole, cholinergic receptor driving increase in [Ca(2+)](i) is M3.