LOCATION OF NITRIC-OXIDE SYNTHASE IN THE DEVELOPING AVIAN CILIARY GANGLION

A study has been made of the distribution of nitric oxide synthase (NO S) in the developing avian ciliary ganglion. Nicotinamide adenine dinu cleotide phosphate diaphorase (NADPH-d) activity first appeared in cil iary neurones at embryonic day 10 (E10). The number of NADPH-d positiv e neurones appeared maximal at this age and thereafter declined; at po st hatched day 4 (P4) these neurones were found predominately in the p eriphery of the ganglion. At the light microscope level the NADPH-d st ain appeared throughout the cell soma of the ciliary neurones. This wa s confirmed using tissue culture techniques. Ultrastructural delineati on of horseradish peroxidase-labelled NOS antibodies was also found in the calyx where it was bound to the membranes of the endoplasmic reti culum as well as to the outer membranes of mitochondria. This distribu tion of NOS in the soma and calyx is consistent with the physiological role of NO as a co-transmitter and retrograde messenger that regulate s the quantal secretion of the principal transmitter, acetylcholine, f rom the calyx.