Endormement vago-aortique après section sagittale médiane du tronc cérébral et après administration de p-chlorophénylalanine, ou destruction des noyaux du raphé

Abstract

Vago-aortic sleep after midsagittal section of the brain stem and administration of p-chlorophenylalanine, or after destruction of the raphe nuclei Vago-aortic sleep (cortical synchronization and myosis) triggered by vago-aortic stimulation has been tested in the ‘encèphale isolé’ (EI) cat before and after midsagittal section of the brain stem or suppression of the tryptaminergic mechanisms of the raphe nuclei. A midsagittal section, extending from the caudal bulbar area to the caudal mesencephalic level, does not prevent either the myosis or the cortical synchronizations triggered by the vago-aortic stimulation: the synchronizing pathway does not cross the midline until at least the caudal mesencephalic level and does not directly imply the nuclei obscurus, pallidus, magnus and pontis of the raphe. The tryptaminergic system inactivation was performed (in acute as well as in chronic cat) by electrolytic lesions localized at the level of the brain stem serotonophoric somas, or by the use of p-chlorophenylalanine (PCPA), or by the association of these two methods; in all cases vago-aortic synchronizations occurred; however, they were more or less easily obtained depending upon the experimental conditions: the tryptaminergic activities are not necessary for the onset of vago-aortic synchronization. The lower the level of reticular activity (hypocapnia, minute doses of Nembutal, reticular lesions), the easier it was to obtain vago-aortic synchronizations in animals with raphe system destroyed and pretreated with PCPA. The raphe nuclei could inhibit the waking system; this hypothesis is discussed.