Seasonal changes in vasopressin in the brain of the garden dormouse (Eliomys quercinus L.)

Abstract

The distribution of vasopressin in the brain of the garden dormouse (Eliomys quercinus L.) was examined by immunocytochemistry at different times of the year. In spring-summer, sexual dimorphism in the density of vasopressin labeling was observed in several areas of the brain. In these regions, such as the lateral septum and the nucleus of the vertical limb of the diagonal band of Broca, male garden dormice showed more vasopressin immunoreactivity than their female counterparts. In autumn-winter, at the time of hibernation, vasopressin was undetectable in the sexually dimorphically innervated brain regions in males as well as females. In early spring, there was large variation in vasopressin staining in the male brain, whereas the female brain was consistently lacking in vasopressin labeling. In brain regions that exhibited no sexually dimorphic innervation in the summer, vasopressin labeling remained the same throughout the year. The difference in the amount of vasopressin immunoreactivity in males in summer and winter correlated significantly with differences in testes weight. In early spring, because of interindividual variations in the start of sexual activation, testes size does not correlate with the density of vasopressin immunoreactivity. Similar seasonal variations in density of vasopressin labeling in the brain were also observed in the European hamster (Cricetus cricetus). In this animal, central vasopressin infusion during the winter prevents hibernation. The presence of a similar pattern of changing vasopressin content in another hibernator, the garden dormouse, suggests an important role for this neuropeptide in seasonal functions.(ABSTRACT TRUNCATED AT 250 WORDS)