Study of the spinal cords of the sturgeon Acipenser schrenckii, gar Lepisosteus oculatus, and goldfish Carassius auratus by morphological, immunohistochemical, and biochemical approaches.

Little is known about the spinal cords of phylogenetically ancient actinopterygeans. The spinal cords of the chondrostean Acipenser schrenckii (Amur sturgeon), holostean Lepisosteus oculatus (spotted gar), and teleost Carassius auratus (goldfish) were, therefore, analyzed by immunohistochemistry, electron microscopy and two-dimensional gel electrophoresis. Morphology showed numerous similarities between sturgeons and gars. In both, a dorsal column between the two dorsal horns was lacking, giving the grey matter an inverted Y-shape. In goldfish, a small dorsal column was seen, the grey matter occupied a larger area, neuronal density was much higher, and a ventral commissure was apparent, which was absent in sturgeons and gars. In the white matter of sturgeons and gars, small caliber axons predominated, whereas larger axons were frequent in goldfish. Choline acetyltransferase immunoreactive neurons were prevalent in the ventral horns of all three fish, mainly in motoneurons, but stained fibers were only found in sturgeons and gars. gamma-aminobutyric acid positive cells were seen in both the ventral and the dorsal horns of all three fish. Distribution of serotonin (5-HT) and tyrosine hydroxylase (TH) immunoreaction was similar in sturgeons and gars, being located in both the ventral and the dorsal horns. In goldfish, 5-HT label was confined to the ventral horn and TH label was mainly observed in a cell group located ventromedially. Two-dimensional gel electrophoresis showed a gradual increase in protein number from sturgeons to gars to goldfish. In conclusion, the spinal cords of sturgeons and gars share many morphological and chemical features, distinguishing them from the goldfish spinal cord.