M.L.H.J. Hermes

Induction of arousal in hibernating European hamsters (Cricetus cricetus L.) by vasopressin infusion in the lateral septum.

Vasopressin immunostaining in the lateral septum of the European hamster (Cricetus cricetus L.) disappears in autumn, at the time of the first appearance of hypothermic periods characteristic to hibernation. Previous results have shown that chronic administration of vasopressin in the lateral septum during winter prevents the expression of hypothermic periods, suggesting a role for this peptide in hibernation. It is now observed that acute infusion of vasopressin, and in 50% of the cases, of a specific vasopressin V1 receptor agonist, during a hypothermic period results in an immediate termination of hypothermia. Infusion of oxytocin or a vasopressin V2 receptor agonist were without effect. The results indicate that the seasonal variation in central vasopressin activity, possibly through an interaction with V1 receptors, may play an important role in the expression of hibernation in the European hamster.

Oxytocin Neurotransmission in the A1‐area of the Brainstem Induces Hormonal Vasopressin Release in Rats

To investigate the role of the oxytocin innervation of the caudal ventrolateral medulla, immunocytochemical techniques were used to demonstrate the presence of oxytocin fibres and terminals in close apposition to noradrenergic neurons of the A1‐area.

Circadian Organization of the Autonomic Nervous System

Life on our planet is mainly dependent on the presence of our sun, which provides us daily with the energy we need for survival. It is, therefore, not surprising that most organisms have developed a system that allows them to synchronize their (metabolic) activity with the daily appearance of the sun. In more complex organisms, these daily cycles are also responsible for the organization of multiple-day rhythms, such as the weekly, monthly, or yearly reproduction cycles.