[Relationship between the spawning process and quantitative ultrastructural analysis of the neurosecretory elements of the neurohypophysis of female Acipenser güldenstädti sturgeon].

Quantitative studies have been made on functional condition of neurosecretory terminals in the neurohypophysis of sturgeon females during upstream migration, soon after spawning and 3 or more weeks after the latter. Electronmicroscopically, within each of the 3 types if neurosecretory terminals (A1, A2, B) certain forms were distinguished which correspond to separate phases of the secretory cycle; relative amounts of these forms were determined. Functional correlation in the activity of peptide- (A1, A2) and monoaminergic (B) terminals was observed which reveals itself in synchronous increase of the activity of peptidergic and the decrease in the activity of monoaminergic terminals immediately after spawning. At later stages, inactivation of all the 3 types of terminals takes place. Functional significance of this correlation is discussed in relation to double (peptide- and adrenergic) control of the activity of visceral organs during realization of protective and adaptive reactions of the organism under such natural stress conditions, as spawning.