Ultrastructural localisation of NADPH-d/nNOS expression in the superior cervical ganglion of the hamster

This study examined NADPH-d and nNOS expression in the SCG of hamsters. By light microscopy, numerous NADPH-d/NOS positive processes were widely distr ibuted in the ganglion. Ultrastructurally, the NADPH-d reaction product was associated with the membranous organelles of neuronal soma, dendrites, mye linated fibres, small granular cells, and axon profiles bearing agranular v esicles. The NOS immunoreaction product, on the other. hand, was localised in the cytoplasm of principal neurons and dendrites. Some of the NADPH-d/NO S labelled processes formed junctional contacts including synapses or zonul ae adherentia. Compared with the neurons, the nonneuronal cells in the gang lion, namely, macrophages, satellite cells and endothelial cells were label led by NADPH-d but devoid of nNOS immunoreaction product. The results sugge st that the NADPH-d/NOS positive fibres in the SCG originate not only from the pi-ejecting fibres of the lateral horns of thoracic spinal cord, but al so from the principal neurons and small granular cells; some may represent visceral afferent fibres. Electron microscopic morphometry has shown that a bout 67% of the principal neurons contain NADPH-d reaction product, and tha t the majority were small to medium sized neurons based on cross-sectional areas in image analysis. On the basis of the present morphological study, i t is concluded NO is produced by some local neurons and possibly some nonne uronal cells in the SCG as well as some fibres of extrinsic origin. In this connection, NO may serve either as a neurotransmitter or neuromodulator.