Chronic stress during paradoxical sleep deprivation increases paradoxical sleep rebound: Association with prolactin plasma levels and brain serotonin content

Previous studies suggest that stress associated to steep deprivation methods can affect the expression of steep rebound. in order to examine this association and possible mechanisms, rats were exposed to footshock stress during or immediately after a 96-h period of paradoxical steep deprivation (PSD) and their steep and heart rate were recorded. Control rats (maintained in individual home cages) and paradoxical steep-deprived (PS-deprived) rats were distributed in three conditions (1) no footshock - NF; (2) single footshock - SFS: one single footshock session at the end of the PSD period (6-8 shocks per minute; 100 ms; 2 mA; for 40 min); and (3) multiple footshock - MFS: footshock sessions with the same characteristics as described above, twice a day throughout PSD (at 7:00 h and 19:00 h) and one extra session before the recovery period. After PSD, animals were allowed to sleep freely for 72 h. Additional groups were sacrificed at the end of the steep deprivation period for blood sampling (ACTH, corticosterone, protactin and catecholamine levels) and brain harvesting (monoamines and metabolites). Neither SFS nor MFS produced significant alterations in the steep patterns of control rats. All PS-deprived groups exhibited increased heart rate which could be explained by increased dopaminergic activity in the medulla. As expected, PS deprivation induced rebound of paradoxical steep in the first day of recovery; however, PSD + MFS group showed the highest rebound (327.3% above the baseline). This group also showed intermediate Levels of corticosterone and the highest levels of protactin, which were positively correlated with the Length of PS episodes. Moreover, paradoxical steep deprivation resulted in elevation of the serotonergic turnover in the hypothalamus, which partly explained the hormonal results, and in the hippocampus, which appears to be related to adaptive responses to stress. the data are discussed in the realm of a prospective importance of paradoxical steep for processing of traumatic events. (C) 2008 Elsevier B.V. ALL rights reserved.Associacao Fundo de Incentivo a Psicofarmacologia (AFIP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Federal de São Paulo, Dept Psychobiol, BR-04024002 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, BR-04024002 São Paulo, BrazilFAPESP: FAPESP/CEPID#98/14303-3FAPESP: FAPESP#04/02213-2Web of Scienc