Muscarinic acetylcholine receptors of the chick amnion

作者：Manukhin B N^*; Boiko O V

来源：Biology Bulletin, 2008, 35(2): 187-193.

DOI：10.1134/S1062359008020131

The presence of muscarinic (M) acetylcholine receptors in the noninnervated chick amnion makes it possible to analyze their functioning with presynaptic effects excluded. The M receptors of the amnion mediating its contraction were identified by testing with selective antagonists: pirenzepine for M-1, methoctramine for M-2, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) for M-3, and tropicamide for M-4 receptor subtype. All antagonists acted as competitive inhibitors of M-acetylcholine receptors. With respect to cholinolytic activity estimated from the response to carbacholine (CBC) (-logIC(50)), the antagonists could be arranged in the following series: 4-DAMP (8.29) > tropicamide (6.97) > pirenzepine (5.85) > methoctramine (5.63). In addition, the effect of forskolin (5 mu M), activator of adenylate cyclase (AC), was unidirectional with approximate to-adrenergic agonists; it blocked CBC-induced contractile activity of the amnion, whereas phospholipase C (1.25 U/ml) stimulated this activity. These data suggest that CBC-or acetylcholine (ACh)-induced contractile activity of the amnion is mediated by M-3 acetylcholine receptors. Evaluation of contractile response to ACh by the tonic component usually revealed one pool of M-3 acetylcholine receptors. One pool was also revealed after treatment with 4-DAMP, with the Hill coefficient being increased (ACh, n = 1.07; ACh against the 4-DAMP background, n = 1.48). It is possible to detect two pools of M-3-acetylcholine receptors on the basis of either phase-frequency or tonic response, i.e., independently of the test parameter.

• 出版日期2008-4