Spontaneous and evoked oscillations of cytosolic calcium in the freshly prepared ciliary epithelial bilayer of the rabbit eye

Under confocal microscopy, calcium imaging of the isolated secretory ciliary epithelium, especially the inner layer, non-pigmented epithelium (NPE), revealed spontaneous calcium oscillations in multiple patterns. Oscillations induced by stimulation of the muscarinic receptor have an onset that coincides with synthesis and release of InsP(3). Caffeine (5 mM) induced a calcium transient and blocked spontaneous and (0.1 mM) muscarine induced oscillations. Thapsigargin (1 mu M) prevented a muscarinic response. Muscarine and caffeine induced transients have significantly greater amplitude in NPE than in PE (outer layer, pigmented epithelium). Calcium transients and frequencies of spontaneous oscillations are greater in NPE than PE. In NPE muscarine induced oscillations are observed with higher frequencies than the spontaneous ones: gamma-0.24 +/- 0.05Hz (8) versus 0.08 +/- 0.01Hz (18). These repetitive responses, spontaneous and receptor coupled, reflect intracellular coding of information. A calcium signal may contribute to the regulation of aqueous humor formation. (C) 1996 Academic Press, Inc.