Characteristics of the Functional State of the Hypothalamo-Hypophyseal-Adrenocortical System in Krushinskii–Molodkina Rats

Abstract

The aims of the present work were to assess interstrain differences in the functional state of the hypothalamo-hypophyseal-adrenocortical system (HHACS) in intact Wistar rats and the Krushinskii–Molodkina (KM) strain, which constitutes a genetic model of reflex audiogenic epilepsy and to analyze the dynamics of changes in the HHACS in KM rats during and after convulsive seizures. The results show that KM rats display a reduced level of activity of corticoliberinergic neurons due to an increase in the inhibitory influence of GABAergic neurons. The anterior lobe of the hypophysis showed increases in proopiomelanocortin (POMC) and adrenocorticotrophic hormone (ACTH) contents. Basal blood ACTH and corticosterone levels in KM and Wistar rats were no different. Thus, these data provide evidence of impairments to the interaction of the hypothalamus and hypophysis in KM rats, which may evidently be among the possible mechanisms supporting the maintenance of blood hormone concentrations at levels characteristic of control rats of the maternal Wistar strain. Single convulsive seizures in KM rats led to increases in corticoliberin and vasopressin release in the portal circulation and ACTH in the systemic circulation at the clonic-tonic stage, which developed 6–10 sec after the moment of presentation of the sound signal. A prolonged increase in the blood corticosterone level lasting 24 h was seen. Sound stimulation with the same parameters in Wistar rats did not lead to any significant changes in ACTH or blood corticosterone concentrations. Thus, the data obtained here suggest a specific nature of HHACS activation in KM rats due to the propagation of epileptiform activity in the brain; the results provide evidence of the involvement of the HHACS in mediating convulsive activity.