Prostaglandins E₁ and E₂, but not F_2α or Latanoprost, Inhibit Monkey Ciliary Muscle Contraction

Abstract

Purpose: To investigate the effects of prostaglandin (PG) E₁, E₂, F_2α, and latanoprost acid on the electrically evoked contractile response of isolated rhesus monkey ciliary muscle. Methods: Longitudinal ciliary muscle preparations from rhesus monkeys were mounted in an organ bath, and tension changes were recorded by an isometric transducer. Electrical field stimulation (100 Hz, 0.3 ms, 10 V) was applied through a pair of platinum plate electrodes. Results: The ciliary muscle produced atropine-sensitive excitatory contraction in response to field stimulation. PGE₁ and PGE₂ (1 μ M) attenuated the contraction to levels that were 68% and 65.1%, respectively, of the normal amplitude. However, PGF_2α and latanoprost acid (1 μ M) did not significantly change the response amplitude. Conclusions: Our results indicate that PGF_2α and latanoprost acid do not interact with the prostanoid receptor involved at the pre- and/or postsynaptic site. Therefore, it is unlikely that the hypotensive action by these agents is due to relaxation of the ciliary muscle.

KEYWORDS:

• ciliary muscle
• intraocular pressure
• latanoprost
• prostaglandin
• uveoscleral outflow