Muscarinic cholinergic receptor subtypes in the pigeon bursa of Fabricius: a radioligand binding and autoradiographic study

• Published in: Journal of neuroimmunology Vol. 66; no. 1; pp. 23 - 28
• Main Authors: Ricci, Alberto, Bronzetti, Elena, Felici, Laura, Ciriaco, Emilia, Vega, JosèA., Germanà, Giovanni
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.1996
• Subjects: Animals; Autoradiography; Binding Sites; Bursa of Fabricius; Bursa of Fabricius - metabolism; Male; Muscarinic receptor subtypes; Pigeon; Quinuclidinyl Benzilate - metabolism; Radioligand Assay; Radioligand binding; Receptors, Muscarinic - metabolism; Temperature; Time Factors; Tissue Distribution; Bursa of Fabricius; Autoradiography; Radioligand binding; Pigeon; Muscarinic receptor subtypes
• ISSN: 0165-5728; 1872-8421
• DOI: 10.1016/0165-5728(96)00012-4

The pharmacological profile and the anatomical localisation of muscarinic cholinergic receptor subtypes were studied in the pigeon bursa of Fabricius, using radioligand binding and autoradiographic techniques with [ 3H]quinuclidinyl benzilate (QNB) as a ligand. [ 3H]QNB was specifically bound to sections of bursa of Fabricius. The binding was time-, temperature- and concentration-dependent. The dissociation constant was 0.31 ± 0.02 nM, and the maximum density of binding sites averaged 38 ± 2.5 fmol/mg protein. The pharmacological profile of [ 3H]QNB binding to sections of pigeon bursa of Fabricius was consistent with the labelling of M 2, M 3 and M 4 muscarinic receptor subtypes. Light microscope autoradiography showed the localisation of [ 3H]QNB binding sites in the medulla, in follicular septa, in the cortico-medullary border and in lesser amounts in the cortical layer. The functional significance of these receptors should be clarified in future studies.