Circulatory reflex responses during the initial stage of feline endotoxin shock.

Cardiovascular and autonomic nervous responses to an injection of E. coli endotoxin were followed for up to 15 min. in cats anesthetized with chloralose and given artificial respiration. Within 60 seconds, endotoxin induced a drop of aortic pressure, with simultaneous cardiac acceleration and slight central venous hypertension. There was an associated, almost complete cessation of the aortic arch baroreceptor afferentation. The cardiac sympathetic efferentation increased up to 1.4 times the control level at its maximum. The splenic sympathetic efferentation increased up to 10.6 times the control level at the end of the 15 min period, when the other parameters studied showed a trend to control level. The sympathetic autonomic system seems to be activated through cardiovascular receptors sensing hemodynamic changes touched off by endotoxin-induced release of vasoactive substances.