Eye movements and abducens motoneuron behavior during cholinergically induced REM sleep.
OBJECTIVE
The injection of cholinergic drugs in the pons has been largely used to induce REM sleep as a useful model to study different processes during this period. In the present study, microinjections of carbachol in the nucleus reticularis pontis oralis (NRPO) were performed to test the hypothesis that eye movements and the behavior of extraocular motoneurons during induced REM sleep do not differ from those during spontaneous REM sleep.


METHODS
Six female adult cats were prepared for chronic recording of eye movements (by means of the search-coil technique) and electroencephalography, electromyography, ponto-geniculo-occipital (PGO) waves at the lateral geniculate nucleus, and identified abducens motoneuron activities after microinjections of the cholinergic agonist carbachol into the NRPO.


RESULTS
Unilateral microinjections (n = 13) of carbachol in the NRPO induced REM sleep-like periods in which the eyes performed a convergence and downward rotation interrupted by phasic complex rapid eye movements associated to PGO waves. During induced-REM sleep abducens motoneurons lost their tonic activity and eye position codification, but continued codifying eye velocity during the burst of eye movements.


CONCLUSIONS
The present results show that eye movements and the underlying behavior of abducens motoneurons are very similar to those present during natural REM sleep. Thus, microinjection of carbachol seems to activate the structures responsible for the exclusive oculomotor behavior observed during REM sleep, validating this pharmacological model and enabling a more efficient exploration of phasic and tonic phenomena underlying eye movements during REM sleep.
Márquez-Ruiz
Javier
J
Neurociencia y Comportamiento, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Escudero
Miguel
M
D000010:Abducens Nerve / Q000187:drug effects*; D000818:Animals; D002217:Carbachol / Q000494:pharmacology*; D002415:Cats; D018679:Cholinergic Agonists / Q000494:pharmacology*; D002799:Cholinergic Fibers / Q000187:drug effects; D005133:Eye Movements / Q000187:drug effects*; D005260:Female; D008845:Microinjections; D009046:Motor Neurons / Q000187:drug effects*; D009434:Neural Pathways / Q000503:physiopathology; D017286:Polysomnography; D011149:Pons / Q000187:drug effects*; D012154:Reticular Formation / Q000187:drug effects*; D012815:Signal Processing, Computer-Assisted; D012895:Sleep, REM / Q000187:drug effects*; D014851:Wakefulness / Q000502:physiology
D018679:Cholinergic Agonists; D002217:Carbachol