[Cytoarchitectonic and neurochemical properties of spinal cord in teleost fishes].

Traditional neuromorphological and NADPH-diaphorase methods were used to study the topography, morphology and neurochemical organization properties of spinal cord in teleosts fishes. The heterogeneous population of NO-producing motoneurons was revealed in the motor column of spinal cords from studied species. Dendrites of primary motoneurons formed rich plexus at the spinal segment periphery. This morphological pattern is determined by translational motion of the fishes in the water (trunk-tail movement), and has no connection with the origin of upper and lower extremities. The NO-producing capacity of spinal motoneurons shows their connection with premotor NO-ergic brain system, including over situated motor centers of reticular formation and descending projections of giant steam neurons (Mauthner and Muller cells). The NO-producing Rohon-Berd neurons were found in the dorso-medial part of spinal cord from studied fishes. These cells with the ascending propriospinal targets form spinal nociceptive system. Thus, the sense Rohon-Berd cells and most motor neurons of studied bony fishes are nitric oxide synthesizing ones. Spinal cord NO-synthesizing territories are situated in concordance with dorso-ventral histochemical gradient. Spinal cord interneurons of these fishes produce nitric oxide selectively. The quantity of NO-synthesizing reticular cells is determined by two main factors: the connection with the specialized neurochemical complexes, where NO is a specific neuromodulator, and individual properties of spinal cord structure directed by conditions of morphoadaptation.