Serotonergic hypothesis of sleepwalking
Section snippets
The characteristic of sleepwalking
Sleepwalking (somnambulism) is one of the most common parasomnias and refers to various complex motor behaviours, including walking, that are initiated during deep (stages 3–4) non-rapid-eye-movement (NREM) sleep. Some episodes may be limited to sitting up, fumbling, picking at bedclothes, and mumbling but usually sleepwalkers usually stand up and walk around quietly and aimlessly. Occasionally, they become agitated, with thrashing about, screaming, running, and aggressive behavior [1]. The
Etiology of sleepwalking
Despite widespread prevalence of sleepwalking, its etiology and pathophysiology are not well understood [2], [3]. To date, genetic, developmental, organic, and psychological factors have been proposed as causes of sleepwalking and somnambulism episodes can be triggered by fever, medication with some drugs, stress and major life events [4]. Recently, Bassetti et al. [1] proposed that sleepwalking could result from activation of thalamocingulate pathways and persisting deactivation of other
The role of serotonergic neurons in chemoreception
Cell bodies containing serotonin (5-hydroxytryptamine; 5-HT) are localized in two major groups in or near the brain stem raphe nuclei [7]. The rostral group, localized in the pons/mesencephalon, contains the dorsal (DRN) and the median (MRN) raphe nuclei whereas the caudal group, localized in the medulla, is comprised primarily of the nuclei raphe magnus, obscurus and pallidus (NRM, NRO and NRP, respectively). Medullary 5-HT neurons are located proximally within the vascular tree, close to
The role of serotonin in control of motor activity
According to Jacobs and Fornal [9], the primary role of brain serotonergic system is facilitation of gross motor movement. It has been shown, using various methods, that serotonin exerts facilitatory effects on motoneurons. In vivo application of 5-HT in the vicinity of spinal motoneurons or systemic injection of 5-HT precursors leads to an increase in motoneuronal excitability, increases tonic muscle electromyogram (EMG) activity and facilitates some spinal motor reflexes [10]. Large body of
The limited role of serotonin in arousal
Although the discharge rate of raphe 5-HT neurons is grossly correlated with level of arousal across the sleep-wakefulness cycle, it has also been shown that activity of serotonergic neurons modulating the motor system can be dissociated from the arousal. In cats with lesions of the dorsomedial pons, the activity of DRN 5-HT neurons was similar to that in normal cats during waking and NREM sleep and these pontine lesioned animals displayed normal waking behavior [11]. However, during REM sleep
The role of serotonin in pathophysiology of sleepwalking
We would like to put forward a hypothesis that serotonergic system may be a link between abnormal breathing and motor activity during sleep. The 5-HT neurons can play such a role because serotonin provides a tonic excitatory drive that gates afferent inputs to motoneurons, the activity of raphe neurons can be dissociated from the level of arousal, and raphe neurons are activated by hypercapnic acidosis. Normally, the responsiveness of 5-HT neurons to systemic CO2 stimulation is greatly reduced
Conclusions
In summary, cerebral serotonergic system may play an important role in pathophysiology of sleepwalking. This hypothesis is supported by the fact that several factors known to precipitate episodes of sleepwalking activate serotonergic system. The higher prevalence of other sleep disorders, including night terrors and enuresis, in sleepwalkers suggest that sleepwalking may be a part of a more generalized sleep disturbance and can share a common pathophysiological substrate [35]. Therefore,
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2013, PsychosomaticsCitation Excerpt :The preservation of stage N3 (slow wave) sleep that occurs with zolpidem relative to traditional benzodiazepines might increase the likelihood of NREM parasomnias, as these events most commonly arise from slow wave sleep.15,16 Serotonergic dysfunction may be involved in pathogenesis of sleep walking.17 The findings of an epidemiologic study suggest that SSRI use was particularly associated with SRED.