Effects of adrenergic agonists and cyclic AMP on the short-circuit current across the isolated rabbit iris-ciliary...

Epinephrine, isoproterenol and norepinephrine (10(-6) M - 10(-4) M) reduced the short-circuit current (SCC) across the isolated rabbit iris-ciliary body when added to the blood side (pigmented layer) bathing solution but were without effect when added to the aqueous side (non-pigmented layer) bathing solution. The effect was observed in both HCO-3-rich and HCO-3-free solutions, although it was smaller in the latter. Propranolol and phentolamine (10(-5) M) partially blocked the action of the adrenergic agonists, 8Br-cAMP (1 mM), on the other hand, stimulated the SCC when added to either bathing solution. The apparent contradiction between these results is explained on the basis of separate cyclic AMP compartmentalization in the two epithelial cell layers and the lack of adrenoceptors in the non-pigmented layer.