[Characteristics of contraction force of bovine ciliary muscles caused by cholinergic agent].

We studied the contractions caused by the cholinergic agent carbachol on bovine ciliary muscles. Ciliary muscle strips (width 4 mm x length 6 mm) were prepared in the directions of the longitudinal and circular muscles. Contractions were measured with an isometric tension recorder. The concentration for 50% effective dose was 10(-7) M carbachol, and maximum contraction was obtained at 3 x 10(-6) M. Also, maximum contraction was obtained at a resting tension of 600 mg for the longitudinal direction and 400 mg for the circular direction. At a resting tension of 400 mg and concentration of 10(-5) M, average contraction for the longitudinal direction (L) was 335 +/- 106 mg (mean +/- SD, n = 20) and 104 +/- 52 mg (mean +/- SD, n = 20) for the circular direction (C). The ratio between L and C was about 3:1. The results suggest that bovine ciliary muscles have more ability to perform accommodation than in previous reports, and that the magnitude of contractions depends on the direction of the ciliary muscle fibers.