Endocrine Abstracts

Neurohypophysial hormone, arginine–vasopressin (AVP) concentrations in human plasma and in the plasma, and hypothalamus of the rat display diurnal variations with rising levels over the hours of sleep. Previous reports indicate that AVP infusions reduce rapid-eye-movement sleep in humans and increase the amount of time spent in waking in rats. Our aim was to determine whether AVP content of the rat hypothalamus is altered by sleep deprivation (S.D.). Adult male Sprague-Dawley rats were acclimated to a 12:12-h light–darkness cycle and were sleep deprived by gentle handling starting at light onset. Hypothalamic samples (n=8–10 per group) were obtained after 4 and 8 h of S.D.and after 1 and 2 h of recovery following 8 h of S.D. Control samples were collected from undisturbed rats at corresponding time points. After extraction, AVP was determined by means of radioimmunoassay. The changes in AVP during and after S.D. were evaluated with respect to the time-matched control samples by means of two-way ANOVA. Hypothalamic AVP contents differed significantly between the control groups and the sleep deprived animals. AVP was normal after 4 h of S.D..and dropped to a low level by the end of h 8 of S.D.. AVP was significantly suppressed after 1 and 2 h of recovery. Similarly to our data S.D.. induced a significant fall in nighttime plasma AVP in healthy children. Current results confirm that diurnal variations in AVP secretion are in fact associated with sleep thus AVP could play a role in the physiological regulation of sleep.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.