title: Muscarinic cholinergic receptor subtypes in the hippocampus of aged rats.
abstract: In spite of the suggestion of impaired muscarinic function in adult-onset cognitive disorders, data on the expression of muscarinic receptors in the hippocampus as a function of age are inconsistent. One reason may be that the majority of investigations were unable to differentiate the five brain muscarinic receptors subtypes. In this study, using a protocol based on a combination of both kinetic and equilibrium binding approaches, we have assessed the expression and the density of M1-M5 muscarinic cholinergic receptors in the hippocampus of Fisher 344 rats aged 6, 15 and 22 months. An age-related decrease of the density of M1 receptor was found in pyramidal neurons of the CA1 subfield. In this area, other subtypes of muscarinic receptors were unchanged with the exception of a loss of M2 receptor in the radial layer. In the CA3 subfield, receptor changes involved M2, M3 and M5 subtypes, whereas in the dentate gyrus, the main changes affected M1 and M2 receptors of the granular layer and M2 and M3 receptors of the molecular layer. The above findings indicate that analysis of age-related changes of different muscarinic cholinergic receptors might represent a useful contribution to identifying the basis of cholinergic neurotransmission impairment in adult-onset cognitive dysfunction.
authors.affiliation: Sezione di Anatomia Umana, Dipartimento di Scienze Farmacologiche e Medicina Sperimentale, Università di Camerino, Via Scalzino 3, 62032, Camerino, Italy. khosrow@cambio.unicam.it
authors.forename: Seyed Khosrow
authors.initials: SK
authors.lastname: Tayebati
authors.forename: Francesco
authors.initials: F
authors.lastname: Amenta
authors.forename: Dahuk
authors.initials: D
authors.lastname: El-Assouad
authors.forename: Damiano
authors.initials: D
authors.lastname: Zaccheo
mesh_terms: D000375:Aging / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D006624:Hippocampus / Q000378:metabolism* / Q000473:pathology; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010890:Pirenzepine / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D043643:Receptor, Muscarinic M1; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D043588:Receptor, Muscarinic M4; D043642:Receptor, Muscarinic M5; D011976:Receptors, Muscarinic / Q000378:metabolism*
chemical_list: D018727:Muscarinic Antagonists; D043643:Receptor, Muscarinic M1; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D043588:Receptor, Muscarinic M4; D043642:Receptor, Muscarinic M5; D011976:Receptors, Muscarinic; D010890:Pirenzepine