The aim of the present work was to study the secretory activity of vasopressinergic neurons in the hypothalamus in Krushinskii–Molodkina rats, which have a predisposition to audiogenic epilepsy, in normal conditions and during audiogenic convulsive seizures. Serum vasopressin and neurohypophyseal neurophysin II levels were compared in Wistar and Krushinskii–Molodkina rats. These studies demonstrated a decreased blood vasopressin level and an increased neurohypophyseal neurophysin II level in rats predisposed to audiogenic epilepsy, which is evidence for inhibition of the release of vasopressin into the blood. Analysis of vasopressin levels at different stages of convulsive seizures revealed a significant increase in the plasma vasopressin concentration at the clinic-tonic stage of convulsive seizures. Thus, this is the first study demonstrating that Krushinskii–Molodkina rats predisposed to audiogenic epilepsy have lower levels of vasopressinergic neuron secretory activity than sound-insensitive Wistar rats. A significant increase in plasma vasopressin at the clonic-tonic stage of convulsive seizures is evidence that the vasopressinergic neurosecretory system has a role in mediating audiogenic convulsive seizures.