Carotid sinus baroceptor modifications associated with endotoxin shock

¹ Department of Physiology, University of Minnesota Medical School, Minneapolis, Minnesota

Carotid sinus baroceptor responses were studied in dogs before and after administration of shock-producing quantities of E. coli endotoxin. Responses were characterized as the relationship between intrasinusal stimulus pressure and baroceptor nerve discharge frequency. Both constant and pulsating pressure stimuli were used. After endotoxin administration and the onset of endotoxin shock it was found that postendotoxin discharge frequencies exceeded control discharge frequencies for most pressures. These response shifts result in a resetting of the hemoregulatory barostatic mechanism to regulate blood pressure to a new and hypotensive level. It is concluded that in the later phases of endotoxin shock, the reflex modification may play the predominant role in maintaining hypotension and that barostatic resetting partially explains the poor compensatory response to the initial profound hypotension after endotoxin administration.