Differential smooth muscle-like contractile properties of trabecular meshwork and ciliary muscle.
The contractile properties of bovine trabecular meshwork and ciliary muscle strips were investigated using an electromagnetic force-length transducer for isometric force measurements. Acetylcholine, pilocarpine and aceclidine administration resulted in dose-dependent contractions of trabecular meshwork and ciliary muscle. Absolute forces were approximately 10 times larger in ciliary muscle than in trabecular meshwork. Maximal force evoked by aceclidine (5 x 10(-5) M), when compared to the pilocarpine (5 x 10(-5) M) response, was significantly higher in trabecular meshwork than in ciliary muscle. The results were 172.5 +/- 12.6% (n = 7) and 138.9 +/- 4.0% (n = 8, P less than 0.05), respectively. Depolarization induced by raised external potassium (120 mM), when compared to the acetylcholine response (10(-3) M), resulted in a small contraction of 19.3 +/- 4.2% in trabecular meshwork (n = 5), and of 59.0 +/- 13.7% in ciliary muscle (n = 4, P less than 0.01). Both responses were inhibited by atropine (10(-5) M). The differential potassium effect may be explained by the large number of cholinergic nerve endings in ciliary muscle as compared to trabecular meshwork tissue. Recently, a dissociation between the effects of aceclidine on outflow resistance and accommodation has been described. Our data are consistent with these observations and provide evidence for a direct role of trabecular meshwork contractility in aqueous outflow regulation.
Institut für Klinische Physiologie, Klinikum Steglitz der Freien Universität Berlin, FRG.
A
A
Lepple-Wienhues
F
F
Stahl
M
M
Wiederholt
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002417:Cattle; D002924:Ciliary Body / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology*; D010862:Pilocarpine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011812:Quinuclidines / Q000494:pharmacology; D014129:Trabecular Meshwork / Q000502:physiology*
D011812:Quinuclidines; D010862:Pilocarpine; D001285:Atropine; D000109:Acetylcholine; D011188:Potassium