[Participation of apoptotic proteins in hypothalamic regulation of the population volume of the red-backed vole (Clethrionomys rutilus)].

The content of the antiapoptotic protein Bcl-2 and of the proapoptotic enzyme caspase-3 in the paraventricular nucleus (PVN) of sexually immature red-backed voles is studied in the course of the population cycle. The significant change of the Bcl-2 and procaspase-3 in the PVN neurons is established at all cycle phases. The low volume of population (under the most favorable conditions of the existence of the animals) is revealed to be characterized by the moderately increased or high expression of the Bcl-2 protein alongside with low or moderately increased caspase-3 activity. This is suggested to provide the PVN adequate reaction at the low population volume. At high population volume (under conditions of increased stress in the overcrowded population at the phase of peak and especially of fall), a significant decrease of the Bcl-2 expression is established with simultaneous increase of the caspase-3 activity. The disbalance in synthesis of apoptotic proteins seems to lead to disturbances of PVN functions at phases of peak and fall and, as a consequence, to a decrease of adaptive possibilities of these animals, which might be one of important causes of essential elimination of the animals at the autumn-winter period.

[The characteristics of the formation of the hypothalamo-hypophyseal neurosecretory system in the Arctic lemming Dicostonyx torquatus of Wrangel Island in the postnatal development period]. / Nekotorye osobennosti formirovaniia gipotalamo-gipofizarnoi neirosekretornoi sistemy kopytnogo lemminga Dicrostonyx torquatus ostrova Vrangelia v postnatal'nom periode razvitiia.

Hypothalamo-hypophyseal neurosecretory system (HHNS) of 1-30 days old lemmings Dicrostonyx torquatus from the Wrangel Island in the year of a decreased but still highly dense population was studied by paraldehyde fucshin method and immunohistochemically using antisera to vasopressin and oxytocin. In the period of first two weeks of postnatal development the rate of HHNS formation was found to have significant individual differences and to be slower than HHNS formation in laboratory rats due to less stable and suitable environmental conditions. Like in rats the rate of differentiation of the supraoptic nucleus in lemmings was faster than that of the paraventricular one. Formation of the median eminence was retarded as compared to the hypophyseal posterior lobe. Vasopressin-immunoactive structures appeared earlier than oxytocin-immunoreactive ones both in the neurosecretory centers and in the neurohaemal regions. By 21-30 days the development the HHNS system was practically completed and the levels of maturation of studied structures in different individuals became closer. In this period an accumulation of neurosecretory material was observed in all parts of the HHNS which is probably connected with activation of the system under the condition of stress due to a high population density.