NADPH-DIAPHORASE REACTIVITY IN CILIARY GANGLION NEURONS - A COMPARISON OF DISTRIBUTIONS IN THE PIGEON, CAT, AND MONKEY

Ciliary ganglia from the pigeon, cat, and monkey were investigated for the presence of NADPH-diaphorase reactivity by use of a standard hist ochemical method. In the pigeon, where the ganglion is known to contro l lens and pupil function, and the choroidal vasculature, about one-th ird of the ganglion cells were densely stained and most other somata w ere lightly stained. In some cases, preganglionic terminals with a cap -like morphology were also darkly stained. The pattern of NADPH-diapho rase staining in mammals was very different from that seen in pigeons. In both mammalian species, where the ganglion is known to control len s and pupil function, a small number (less than 2%) of the ganglion ce lls were shown to be densely NADPH-diaphorase positive, revealing thei r neuronal processes. The presence of NADPH-diaphorase positive cells in pigeon, cat, and monkey ciliary ganglia suggests that nitric oxide may be used for intercellular communication in this ganglion, or in li ght of the known importance of nitric oxide in vascular control, some of these positive neurons may participate in the control of choroidal vasodilation.