Characteristics of the experimental reflex sleep induced by vago-aortic nerve stimulation.

1. Electrical stimulation of the baroceptive fibres of the vago-aortic trunks (VA St) reflexly induces, in the Ecéphale isolé (EI) cat preparation, a complete sleep cycle characterized by a progression of all stages of sleep previously described in chronic preparations (slow wave sleep, phasic slow wave sleep, paradoxical or REM sleep). Some qualitative and quantitative characteristics of this "vago-aortic" (VA) sleep are analysed and compared with those obtained in EI cats previously deprived of REM sleep. 2. VA sleep is not simply the consequence of chance occurrences, but the consequence of VA St. It is stimulus-bound, even if the interval between successive stimuli is as short as 7.5 min. Thus it is possible to impose an artificially regular cycle much shorter than the normal one. one. 3. VA St. precipitates the onset of the differrent sleep cycle episodes in the non-REM-deprived EI cat as well as in the REM-deprived EI cat. 4. REM sleep begins rapidly after stimulus onset, so that an experimental reflex REM narcolepsy may be obtained. This effect is particularly noteworthy in REM-deprived cats. In this situation, REM sleep episodes with cataplexy (muscular atonia and areflexia) can immediately follow the onset of stimulation.