Fig. 4. Effect of 5-hydroxytryptamine (5-HT) and ionomycin on the intracellular Ca²⁺ concentration in unidentified ciliary cells in culture. Ciliary cells microinjected with fura-2 dextran were imaged at 1-min intervals in the presence of saline (HS), 5-HT or ionomycin. (A) Representative trace of a ciliary cell that was not affected by a 15 min application of 100 mmol l^–1 5-HT but displayed a rapid rise in the 340/380 ratio in response to 10 µmol l^–1 ionomycin. (B) Representative trace of an unidentified ciliary cell responding to both 100 mmol l^–1 5-HT application and 10 mmol l^–1 ionomycin with an increase in the 340/380 ratio. Dotted lines represent the time at which drug treatments were initiated.