[Seasonal dynamics of the gastric APUD cell count in a hibernator]

Light microscopy was applied to study variation in the composition and number of apudocytes in the gastric epithelium of red-cheeked sousliks over time. During hibernation, the content of serotonin-producing EC cells was elevated. This is in agreement with serotonin involvement in the maintenance of the hibernation state. The number of non-EC cells taking part in digestion, which does not occur during hibernation, was lowered. Spring awakening was accompanied with an increase in the number of non-EC cells and the lack of significant changes in cells. In souslics, which were active in winter, the content of non-cells was high, since the animals continued feeding on, and the content of EC-cells was elevated similarly to that in hibernating animals, which could be explained by genetic dependence. The number of apudocytes in the gastric mucosa was discovered to correlate in the main with the features of their function at different seasons.