Abstract
The autonomic nervous system innervating the stomach and ovaries of the Nile tilapia Oreochromis niloticus was studied in combination with neuroanatomical, fluorescent and electron microscopic, and retrograde-labeling methods. An anatomical examination revealed that the vagal nerve arose from the medulla oblongata and reached the stomach, as a parasympathetic innervation.Several nerves were branched off from the main vagal trunk behind the transverse septum, and one of them reached ipsilaterally at the anterior ovary. The vagal sympathetic and the 3-4 sympathetic ganglion cells, and the parasympathetic ganglion cells in the vagus nerve were involved in autonomic innervation to the two organs. By fluorescent microscopy combined with a formaldehyde-glutaraldehyde method, it was demonstrated that the adrenergic nerve fibers existed in both nerves innervating the stomach and ovaries. Electron microscopic observation revealed that cholinergic and adrenergic types of synaptic vesicles were contained in both nerves, in addition to a few larger vesicles assumed to be peptidergic.Neural origin of the innervation to the stomach was traced to the medulla oblongata, the vagal sympathetic ganglion and the 3-4 sympathetic ganglion by retrograde labeling with cobaltous lysine complex. On the other hand, distribution of the postganglionic cells innervating the ovaries was restricted to the 3-4 sympathetic ganglion, while the origins of the parasympathetic innervation were still obscure.
