PURPOSE The effects of prostaglandin (PG)F2 alpha on the contractile response in the longitudinal and coronal vectors of the isolated rhesus monkey ciliary muscle were studied.
METHODS Fresh rhesus monkey ciliary muscle strips from young and middle-aged animals were mounted in an apparatus capable of monitoring contractile force simultaneously in the two vectors. The responses to PGF2 alpha were measured and compared to those produced with 1 microM carbachol.
RESULTS PGF2 alpha consistently relaxed the carbachol precontracted ciliary muscle in a dose-dependent manner with equal potency and efficacy in both vectors, but it did not alter the tone of muscle strips at resting tension.
CONCLUSIONS The relaxation of precontracted ciliary muscle by PGF2 alpha may help explain how a single topical dose of this prostanoid increases uveoscleral outflow and antagonizes resting myopia in the living monkey.