TY - JOUR
T1 - Characterization of Muscarinic Receptor Involvement in Human Ciliary Muscle Cell Function
AU - Pang, Iok Hou
AU - Matsumoto, Shun
AU - Tamm, Ernst
AU - Desantis, Louis
PY - 1994
Y1 - 1994
N2 - Muscarinic agonist-induced contraction of the ciliary muscle is generally believed to increase aqueous outflow facility and effect accommodation. We used cultured human ciliary muscle cells as a model to study the muscarinic receptor subtype(s) involved in the contractile response of the muscle. Thus, a single cell contraction assay for these muscle cells was developed. And since agonist-induced contraction of smooth muscles is expected to involve the activation of phospholipase C (PLC), we also monitored the PLC activity in these cells. Carbachol caused contraction of the muscle cells in a dose-dependent and time-dependent manner with an estimated EC50 of 1-3 μM. The contractile effect of 100 μM carbachol was antagonized by pretreatment of atropine (1 μM) and 4DAMP (10 nM, antagonist selective for the M1 and M3 receptors) but not by pirenzepine (10 μM, antagonist selective for the M1 receptor), suggesting the involvement of the M3 but not the M1 muscarinic receptor. M3 receptor is also essential for the carbachol-induced PLC activation in the ciliary muscle cells, as indicated by the activity profiles of receptor subtype selective antagonists. For example, the stimulative effect of carbachol (EC50 = 20 μM) was antagonized by pirenzepine (pKi = 6.8), HHSiD (pKi = 7.6), 4DAMP (pKi = 9.5) and methoctramine (pKi < 6). Thus, these results indicate that an M3-like receptor subtype is essential in mediating the muscarinic agonists-induced functional changes, such as PLC activation or muscle contraction, in the ciliary muscle.
AB - Muscarinic agonist-induced contraction of the ciliary muscle is generally believed to increase aqueous outflow facility and effect accommodation. We used cultured human ciliary muscle cells as a model to study the muscarinic receptor subtype(s) involved in the contractile response of the muscle. Thus, a single cell contraction assay for these muscle cells was developed. And since agonist-induced contraction of smooth muscles is expected to involve the activation of phospholipase C (PLC), we also monitored the PLC activity in these cells. Carbachol caused contraction of the muscle cells in a dose-dependent and time-dependent manner with an estimated EC50 of 1-3 μM. The contractile effect of 100 μM carbachol was antagonized by pretreatment of atropine (1 μM) and 4DAMP (10 nM, antagonist selective for the M1 and M3 receptors) but not by pirenzepine (10 μM, antagonist selective for the M1 receptor), suggesting the involvement of the M3 but not the M1 muscarinic receptor. M3 receptor is also essential for the carbachol-induced PLC activation in the ciliary muscle cells, as indicated by the activity profiles of receptor subtype selective antagonists. For example, the stimulative effect of carbachol (EC50 = 20 μM) was antagonized by pirenzepine (pKi = 6.8), HHSiD (pKi = 7.6), 4DAMP (pKi = 9.5) and methoctramine (pKi < 6). Thus, these results indicate that an M3-like receptor subtype is essential in mediating the muscarinic agonists-induced functional changes, such as PLC activation or muscle contraction, in the ciliary muscle.
UR - http://www.scopus.com/inward/record.url?scp=0028331885&partnerID=8YFLogxK
U2 - 10.1089/jop.1994.10.125
DO - 10.1089/jop.1994.10.125
M3 - Article
C2 - 8207320
AN - SCOPUS:0028331885
SN - 1080-7683
VL - 10
SP - 125
EP - 136
JO - Journal of Ocular Pharmacology and Therapeutics
JF - Journal of Ocular Pharmacology and Therapeutics
IS - 1
ER -