Cardiovascular responses of conscious rats to acute intravenous and intracerebroventricular administration of Shigella sonnei endotoxin.

Shigella sonnei lipopolysaccharide (LPS) was injected intravenous (iv) or into the lateral cerebral ventricle (icv) of freely moving rats. Iv injection of 320 micrograms/Kg reduced arterial blood pressure, increased heart rate and did not change pressor response and reflex bradycardia induced by iv bolus injection of phenylephrine (5 micrograms/Kg). Iv injection of 640 micrograms/Kg reduced arterial blood pressure and heart rate, and altered baroreceptor reflexes. Icv injection of LPS (up to 50 micrograms/rat) neither changed resting blood pressure and heart rate nor modified phenylephrine induced pressor response and reflex bradycardia. Results suggest that S. sonnei endotoxin determines cardiovascular changes mainly through baroreceptor resetting. Data also seem to rule out a central nervous system involvement.