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Receptor‐responses in fresh human ciliary muscle
Author(s) -
Lograno Marcello D.,
Reibaldi Alfredo
Publication year - 1986
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1986.tb10827.x
Subject(s) - phentolamine , carbachol , atropine , propranolol , endocrinology , muscarinic acetylcholine receptor , medicine , tetrodotoxin , chemistry , stimulation , angiotensin ii , acetylcholine , isoprenaline , receptor , biology
1 The physiological and pharmacological properties of ciliary muscle isolated from fresh human eyes were investigated. 2 The muscle exhibited no spontaneous activity. Concentration‐dependent contractions in response to carbachol were competitively antagonized by atropine (pA 2 = 8.95). 3 The muscle, precontracted by carbachol (2.7 × 10 −4 M), responded to the application of isoprenaline by concentration‐dependent relaxation blocked by propranolol (3.5 × 10 −9 M to 3.5 × 10 −8 M; pA 2 = 9.15). 4 Angiotensin‐evoked contractions were antagonized by 8‐Ala‐angiotensin II (4.5 × 10 −8 M) in a competitive manner, but were not inhibited by phentolamine or propranolol. 5 Contractions generated by electrical stimulation of the muscle (30 ms, 20 Hz, 60 pulses) were antagonized by atropine (10 −7 M) and tetrodotoxin (6.3 × 10 −7 M). Phentolamine and propranolol did not influence these responses. 6 An increase of the external potassium concentration ([K + ] o ) from 5.4 to 158.8 mM produced a mechanical response, antagonized by atropine, but not influenced by tetrodotoxin, phentolamine or propranolol. 7 The human ciliary muscle appears to carry muscarinic and angiotensin receptors and β 2 ‐adrenoceptors. The estimate of K atropine for muscarinic receptors mediating carbachol‐induced contractions agrees with estimates of K atropine reported for human and rabbit iris.