Scheme of adrenergic, cholinergic, and nitrergic innervations and roles of neurotransmitters in the regulation of nerve and smooth muscle functions in ciliary and ophthalmic arteries. Squares in nerve terminal and smooth muscle represent receptors. Abbreviations: NOS, NO synthase; L-Arg., l-arginine; L-Citru., l-citrulline; ATPex, exogenous ATP; PIP2phosphatidyl inositol bisphosphate; IP3inositol trisphosphate; DG, diacylglycerol; AC, adenylate cyclase; GC, soluble guanylate cyclase0. (From Toda et al., 1999) (391)