Social stability attenuates the stress in the modified multiple platform method for paradoxical sleep deprivation in the rat

The instrumental methods to induce paradoxical sleep (PS) deprivation are s tressful. The modified multiple platform method (MMPM), in which animals ar e placed with new cohorts inside the water tanks, results in augmented ACTH and corticosterone (CORT) responses. We hypothesised that this increased r esponse could be attributed to social instability. In addition, we tested a new environmental control, a grid (GR) placed on the tank floor. Animals w ere submitted to the MMPM for 4 days as socially unstable (UG-coming from s everal cages) or stable groups (SG-coming from one cage), placed either on narrow platforms or on the grid. All UG animals presented higher ACTH level s than their SG counterparts, including home-cage controls. CORT levels of manipulated animals were higher than controls only in the stable group. UG animals presented heavier adrenals than their SG counterparts. Only adrenal s from SG animals placed on the grid were similar to cage controls. SG rats lost less weight than UG animals. While UG animals ate the same amount of chow as home-cage controls, SG animals ate more than control and UG animals . These results suggest that the stress of the MMPM can be attenuated in st able groups. The introduction of a grid on the tank floor may serve an adeq uate environmental control as far as stress related variables are considere d. (C) 2000 Elsevier Science Inc. All rights reserved.