9th multidisciplinary international

Conference of Biological Psychiatry

«Stress and Behavior»

Proceedings of the 9th International Multidisciplinary Conference «Stress and behavior» Saint-Petersburg, Russia, 16-19 May 2005 Editor: Allan V. Kalueff, PhD

CONFERENCE ABSTRACTS 2. SLEEP AND BEHAVIOR

ANALYSIS OF THE SLEEP-WAKE CYCLE STRUCTURE IN YOUNG RATS AFTER SLEEP-DEPRIVATION

AND PHOTOSTIMULATION STRESSES

E.A. Aristakesyan

Institute of Evolutionary Physiology and Biochemistry RAS, St. Petersburg, Russia The influence of chronic stressors such as photostimulation (30 min daily, 10s light :10s pause, 5 days) and acute 6-h sleep deprivation, on a sleep-wake cycle (SWC) in 30—45 day old rats was investigated. Sleep deprivation induced deep stress-like changes in the HPA system (intensification of neurosecretion in supraoptic and paraventricular nuclea), whereas chronic photostimulation exerted more compensated effects (Aristakesyan et al., 2004). The changes of the SWC structure after action these stressing actions were distinct. Sleep deprivation strengthened the phenomenon of «sleep rebound» in a form of the wakefulness (W) reduction in SWC and proportional increase of both slow-wave sleep (SWS), and paradoxical sleep (PS). After photo stimulation, changes in SWC were less robust, and characterized by short-term increase of SWS and PS, rapid recovery of sleep parameters, and increased transient cataleptic stage (CS) in SWC from 2d to 5th stimulation. We have found out the more essential distinctions directly of SWC organization. Usually in young animals, the SWC consist of the wake (W), transient hypnotic or cataleptic stage (CS), superficial and deep SWS, transient stage to paradoxical sleep (TS) and PS. Besides there are the episodes of microactivations (MA) on the background of SWS. We studied the features of transitions from one stage of SWC to another before and after sleep deprivation and photostimulation. Such approach allowed us to evaluate the dynamics of central integrative mechanisms of SWC functioning. The post-deprivation sleep was distinguished by significant subdivision of SWC and increasing of quantity of transitions from W to SWS and from SWS to PS; in common the structure of SWC was changed unessential, but the SWC periods became shorter and more complete. Photostimulations increased the frequency of transition from W to CS (89.1 ± 3.4% vs. baseline 76.4 ± 4.2%). The frequency of transition from W to SWS decrease twice. Together, this suggests that the episodes of CS became longer and more stable. The sharp rise in transitions from CS to the W (18.1 ± 3.4% vs. 64.3 ± 7.1%) confirms this possibility. After photo stimulation, the transition from CS to TS appeared for a first time in SWC. Usually TS was formed only on the background of deep SWS and characterized by appearance alpha- and theta-waves with the high-amplitude slow-wave activity in cortical and hippocampal EEG. If the episodes of MA appeared in TS instead of PS, the deep SWS was developed. The transition from CS to TS in intact rat was absent. It was absolutely absent after post-deprivation sleep, however the frequency of transition from W to SWS omitting the CS was increased significantly. CS became more stable and longer only during the first 20 min of post-deprivation sleep. After that, the periods of CS dropped rapidly. The structure of SWC after deprivation was unaltered. The analysis of the frequency of transitions from one stage of sleep to another allows to consider the sequence of functioning of synchronization and desynchronization systems in CNS. Our data suggest that total sleep deprivation activates both systems of sleep equally, and makes their interaction more rigid. Given that these sleep-regulating systems are evolutionary younger, we may assume that deprivation increases interaction between the thalamocortical SWS- and the reticulo-septo-hippocampal PS- regulating systems. Photostimulation excites the evolutionary ancient systems of SWC integration — hypothalamic (preoptic, paraventricular and suprachiasmatic nuclea), leading to their gradual swing and thus promoting the dissociation of the main mechanisms of SWC organization and transitions from SWS to PS. The dissociation sets free ARAS activity that increases MA quantity. Importantly, the residual reactions after the photostimulated breakdown of SWC (exciting ancient activating systems of sleep integration) are longer that same reactions after the sleep-deprived violation of SWC. The study was supported by the State contract DBS 4/2003 of 15/04/2003.

Psychopharmacol. Biol. Narcol. 2005. Vol. 5, N 2. P. 891-892 Psyhopharmacology & biological narcology

ISSN 1606-8181