L'inhibition bulbaire de l'activite electrodermale

Abstract

Skin potential responses (SPR) elicited by stimulation of the mesencephalic reticular formation are inhibited by simultaneous stimulation of the bulbar reticular formation. The mechanisms of this inhibition, its anatomical origin and its pathways were studied in the anaesthetized cat. The inhibitory points are located within the posterior gigantocellular nucleus, the paramedian reticular nucleus and the ventral reticular nucleus. Partial lesions of the spinal cord, ipsilateral to the stimulated bulbar area, suppress the inhibition of SPR recorded from the ipsilateral hind paw. Inhibition could thus result from the effect of lateral reticulo-spinal fibres on sympathetic spinal neurones. Since the effects on blood pressure of stimulating the bulbar inhibitory areas are variable, the hypothesis that SPR inhibition is a secondary consequence of circulatory variations can be rejected; it also confirms the functional heterogeneity of the bulbar inhibitory structures. Finally, the inhibition of SPR through bulbar stimulation is accompanied, in very lightly anaesthetized animals by strong cortical arousal; hence it can be concluded that SPR inhibition is not a result of diffuse depression of the mesencephalic activating system.