Effect of hypnotic drugs on sleep architecture
Terzano, M.G.; Parrino, L.
Polish Journal of Pharmacology 46(5): 487-490
1994
ISSN/ISBN: 1230-6002 PMID: 7894540 Document Number: 935
It is widely accepted that the conventional polysomnographic parameters (macrostructure of sleep) supply only rough information for clinical purposes. In particular, they often appear inadequate to support a diagnosis of insomnia or the effectiveness of a hypnotic compound. In the past years, attention has been focused on the microstructure of sleep, and especially on the periodic distribution of arousal-related phasic events known as Cyclic Alternating Pattern (CAP). This microstructural rhythm is not only a physiological component of normal NREM sleep, but it also appears highly sensitive in the detection of disturbing factors and drug manipulation. Regardless of the specific context, CAP always translates a condition of arousal instability during sleep. Accordingly, the higher the amount of CAP, the poorer the subjective quality of sleep. In young adults, the physiological amount of CAP Rate (percentage ratio of CAP time to NREM steep time) ranges around 25%, while CAP Rate rises to 55% when sleep is perturbed by continuous white noise (situational insomnia). The analysis of CAP Rate within this framework of situational insomnia is recommended for evaluating the effects of hypnotic drugs under controlled experimental conditions. Therapeutical doses of zolpidem preserve the regular course of sleep both at the macro- and at the microstructural level, when sleep is recorded under basal conditions. In contrast, during acoustic perturbation, zolpidem reduces the pathological amounts of arousal instability by lowering the values of CAP Rate to 38%. The protective activity of zolpidem against noise reverberates especially upon sleep stages 3 and 4, where the disruptive effects of acoustic perturbation are more prominent. The results of this model of situational insomnia have been confirmed in a study carried out on a group of middle-aged insomniacs in which CAP Rate appeared as the only polysomnographic parameter that permitted to discriminate patients from age-matched controls and the zolpidem nights from the placebo nights. Even in this case, the reduction of CAP Rate due to the hypnotic drug was associated with an improved appreciation of sleep quality. The model of situational insomnia based on a controlled source of perturbation can be also used to compare the effectiveness of zolpidem versus other hypnotic agents.
Document emailed within 1 workday
