Increased ACTH and corticosterone secretion induced by different methods of paradoxical sleep deprivation

The methods used to induce paradoxical sleep (PS) deprivation are believed to be stressful. In the present study, two methods were compared in regard to their ability to activate the hypothalamic-pituitary-adrenal (HPA) axis. Animals were placed on multiple large (MLP) or small (MSP) platforms or on single large (SLP) or small (SSP) platforms and blood sampled at the end o f a 4-day period of PS deprivation (experiment 1) or on Days 1 (short-term) and 1 (long-term) of PS deprivation (experiment 2). ACTH and corticosteron e (CORT) levels were determined by RIA. The results of experiment 1 showed that all experimental animals presented increased ACTH response, compared t o controls. CORT levels, however, were only elevated in MSP animals, sugges ting increased adrenal sensitivity. Experiment 2 showed that ACTH levels of MSP animals were higher than MLP and SSP animals, and that animals placed on the multiple platform tanks showed the highest ACTH levels on Day 4 of m anipulation. CORT levels were elevated in the animals kept over small platf orms. and these levels where higher on Day 1 than basal and further elevate d on Day 4 of PS deprivation. These results indicate that the multiple plat form technique induces a distinct activation of the I-IPA axis, and that PS deprivation may act as an additional stressor.