On the Mechanisms of Neuroendocrine Regulation of Fish Reproduction

The participation of the preoptic-postneurohypophysial neurosecretory system in fish breeding was shown by histomorphological, immunohistochemical and electronicmicroscopical researches. The activation of discharge of nonapeptide neurohormones into blood circulation from posterior neurohypophysis at the beginning of spawning, with the following decrease of functional activity of system after it are revealed in every lumpsum (simultaneous) spawning fishes idependently of its season (for example: Acipenser, Lota, Oncorhynchus). The similar reaction of neurosecretory system is observed morphologically also under the conditions of experimental stress–the containing of the adult acipenseridae fish in hypertonic medium. The diphasic reaction of neurosecretory system conforming to stages of an alarm and a resistance of stress, is considered to be the reflection of participation of neurosecretory system in protective-adaptive reactions of an organism to a physiological stress arising at breeding period of lumpsum spawning polycyclic fishes. At monocyclic species at once after spawning there becomes the blockage of function of releasing of neurohormones from posterior neurohypophysis corresponding to supernatural inhibition of system at disstress. The functional role of nonapeptide neurohormones in breeding and the possibility of constructive usage of representation about the spawning as a physiological stress are discussed on the basis of analysis of morpho-functional mechanisms of participation of neurosecretory system in this process.