[Role of prostaglandins in the cooling-induced constriction of the iris sphincter]

Effects of prostaglandins and/or indomethacin on the cooling induced contraction of the bovine iris sphincter muscle were studied in vitro. Cooling of the bathing solution contracted the bovine iris sphincter and the muscle became sensitive to carbachol. Lowering the temperature elevated the muscle tone, while with pretreatment of indomethacin, the elevation was markedly inhibited. Further application of prostaglandins (PGs) such as 10(-8)-3 X 10(-8) M PGE2 reproduced the response induced by low temperature. Effects of cimetidine, methysergide and naloxone were also studied. Whether PGs are exogenously applied or endogenously produced, PGs are responsible for the induction of such responses.