Effect of pinealectomy and a constant high level of circulating melatonin or of 5-methoxytryptamine on the vasopressinergic innervation in the brain of the European hamster (Cricetus cricetus, L).

In the European hamster (Cricetus cricetus,L.) pinealectomy as well as a constant high level of either circulating melatonin or 5-methoxytryptamine induced marked changes in the immunocytochemically demonstrable central vasopressinergic innervation. When compared to control animals, a drastic decrease of AVP-immunoreaction was observed in the diagonal band of Broca, the lateral septum, the medial amygdala and the ventral hypothalamus. The results obtained suggest that part of the central vasopressinergic innervation is involved in pineal dependent seasonal functioning of the animal.