AUTORADIOGRAPHIC LOCALIZATION OF MUSCARINIC CHOLINERGIC RECEPTOR SUBTYPES IN HUMAN PLACENTA

The localisation of M1-M4 muscarinic cholinergic receptor subtypes was investigated in sections of normal human term placenta by light micro scope autoradiography. Muscarinic cholinergic receptor subtypes were f ound almost exclusively in syncytiotrophoblast. Neither other cellular components of placenta, nor blood vessels were labelled. Quantitative analysis of the density of silver grains developed in sections incuba ted with the different protocols for labelling M-1-M-4 receptor subtyp es, revealed that syncytiotrophoblast expresses all subtypes of muscar inic cholinergic receptor investigated. A higher density of binding si tes was found in the apical than in the basal portion of syncytiotroph oblast. The demonstration of muscarinic cholinergic receptors in syncy tiotrophoblast suggests that a cholinergic system may have a role in r egulating transport of compounds from maternal to foetal interface. (C ) 1998 Elsevier Science Ireland Ltd.