Pattern of desynchronized sleep during deprivation and recovery induced in the rat by changes in ambient temperature*

Abstract

The pattern of desynchronized sleep (DS) occurrence in the rat was studied during exposure to an ambient temperature (Ta) of 0 degrees C for 48 h and during a 12 h recovery period at laboratory Ta (23 degrees C) following the first and second 24 h of cold exposure. The exposure to low Ta induces a DS deprivation which is followed, during recovery, by a clear DS rebound. Both the decrease and the following increase in the amount of DS are due to changes in the frequency rather than in the duration of DS episodes. The frequency distribution of the intervals between the end of one DS episode and the beginning of the next (DS interval) has shown that two populations of DS intervals exist, i.e. short DS intervals (</=3 min) and long DS intervals (>3 min). On the basis of this, two types of DS episodes have been identified: the 'single DS episode', which is both preceded and followed by a long DS interval, and the 'sequential DS episode', which is a DS episode occurring within a cluster or a sequence of DS episodes and is characteristically separated by short DS intervals. The occurrence of such sequential DS episodes in a 'DS cluster', allows a high amount of DS to occur without increasing the duration of the DS episode. DS clusters are repressed during cold exposure, when the DS drive is counteracted by the need to thermoregulate, and enhanced during recovery, when the DS drive is unrestrained. In contrast, the occurrence of single DS episodes is much less affected by such different experimental conditions.

The Direct Cooling of the Preoptic-Hypothalamic Area Elicits the Release of Thyroid Stimulating Hormone during Wakefulness but Not during REM Sleep

“…For mammals of a small size the consequences of this outcome may be relevant. For example, when Ta is moved below the inferior limit of thermoneutrality, the rat not only immediately decreases REMS occurrence in a very precise proportion to Ta levels [24], but also shows some adaptive mechanisms which act on a longer term basis: when kept at Ta 0°C for 48 h, animals increase, in the second 24 h period, REMS occurrence well above the low levels reached in the first 24 h period [16]. A similar kind of adaptation is shown by the golden hamster that, following its acclimation to 0°C, displays a daily amount of REMS very close to that normally expressed at thermoneutrality [25].…”

Rapid eye movement (REM) sleep homeostatic regulatory processes in the rat: Changes in the sleep–wake stages and electroencephalographic power spectra

“…Indeed, the occurrence of REM sleep rebound following total sleep deprivation or selective REM sleep deprivation is one of the most common phenomena (Dement, 1960;Vimont-Vicary et al, 1966;Morden et al, 1967;Beersma et al, 1990;Brunner et al, 1990;Endo et al, 1997Endo et al, , 1998Datta et al, 2004). More specifically, some studies have shown that the increase in REM sleep during recovery was proportional to the amount of REM sleep lost in deprivation (Dement et al, 1966;Kitahama and Valatx, 1980;Parmeggiani et al, 1980;Perez et al, 1992;Amici et al, 1994). Finally, some selective REM sleep deprivation studies have shown that during deprivation there are progressively more frequent attempts at transitions into REM sleep, an indication of a strong homeostatic drive for REM sleep (Endo et al, 1997(Endo et al, , 1998Ocampo-Garces et al, 2000;Werth et al, 2002;Datta et al, 2004).…”

The α1 adrenoceptor antagonist prazosin enhances sleep continuity in fear-conditioned Wistar–Kyoto rats

“…Sleep latency (time to the first non-REMS epoch ≥ 15 s), sleep efficiency (total sleep time/total recording time), and total times (min) spent in REMS and non-REMS were measured. REMS was further assessed by partitioning episodes into si-REMS (inter-REMS episode interval > 3 min) and seq-REMS (inter-REMS episode interval ≤ 3 min) (Amici et al, 1994). Using these criteria, total times (min) spent in si-REMS and seq-REMS, as well as the number and mean duration of si-REMS and seq-REMS episodes, were calculated using a program created by Dr. Aaron Pawlyk (2005).…”

“…While the effects of FC on REMS generally have been assessed using standard measures of REMS macroarchitecture, such as the number and average duration of REMS episodes and the total amount of time spent in REMS, the microarchitecture of REMS also has been investigated (Amici et al, 1994; Zamboni et al, 1999). By partitioning total REMS time into sequential REMS (seq-REMS, inter-REMS episode interval ≤ 3 min) and single REMS (si-REMS, inter-REMS episode interval > 3 min), Amici et al (1994) and Zamboni et al (1999) determined that various stressors specifically affect seq-REMS and that episodes of seq-REMS, which are on average of shorter duration than those of si-REMS, occur in clusters. For example, Amici et al (1994) found that the recovery sleep following exposure to cold stress occurred with an increased number of seq-REMS episodes in rats.…”

“…By partitioning total REMS time into sequential REMS (seq-REMS, inter-REMS episode interval ≤ 3 min) and single REMS (si-REMS, inter-REMS episode interval > 3 min), Amici et al (1994) and Zamboni et al (1999) determined that various stressors specifically affect seq-REMS and that episodes of seq-REMS, which are on average of shorter duration than those of si-REMS, occur in clusters. For example, Amici et al (1994) found that the recovery sleep following exposure to cold stress occurred with an increased number of seq-REMS episodes in rats. This finding suggested that studying REMS microarchitectural changes following FC in rodent models might yield new insights into the mechanisms of stress-induced sleep disturbances that may be particularly relevant to PTSD.…”