[Change in serotonin metabolism in the rat brain in response to the repeated stimulus presentation].

The content of serotonin (5-HT), its metabolite 5-hydroxyindoleacetic acid (5-HIAA), monoamine oxidase (MAO) activity and kinetic parameters (K(m) and Vmax) for the reaction of 5-HT deamination, were examined in various regions of the rat brain after repeated presentation of a contextual stimulus. Habituation to the stimulus was accompanied by an increase of 5-HT metabolism and active transport of 5-HIAA in the amygdala, striatum and midbrain, while these changes were not found in the prefrontal cortex and hippocampus. Kinetic studies have revealed that the enhancement of 5-HT deamination by MAO in the brain structures was mediated by different catalytic mechanisms.

[Mechanisms of changes in blood flow distribution between organs in hens during ontogenesis].

Anatomical and histological investigations of large arteries feeding head, extremities and chorioallantoic membrane were carried out in 11-, 14-, and 18-day old chicken embryos and in 1- and 40-day old Shaver chickens. The numerical relationships between an arterial diameter and a body mass; a vessel length, its external diameter and a wall thickness, were determined. Our data demonstrate that walls of large arteries in the anterior and the posterior parts of the chicken embryo body are different in quantity, composition, and maturity of their tissue components, determining the lumen size and hemodynamic conditions in the blood bed.