The effect of endotoxin on heart rate dynamics in diabetic rats

- Systemic endotoxin administration increased the regularity of cardiac rhythm in healthy animals.
- Endotoxemia was associated with impaired responsiveness of isolated atria to cholinergic stimulation in healthy rats.
- Diabetes was associated with development of tolerance to cardiac chronotropic effect of endotoxin in rats.

The effect of endotoxin on heart rate variability (HRV) was assessed in diabetic and controls rats using a telemetric system. Endotoxin induced a reduction in sample entropy of cardiac rhythm in control animals. However, this effect was significantly blunted in streptozotocin-induced diabetic rats. Since uncoupling of cardiac pacemaker from cholinergic control is linked to reduced HRV in endotoxemia, chronotropic responsiveness to cholinergic stimulation was assessed in isolated atria. Endotoxemia was associated with impaired responsiveness to carbacholine in control rats. However, endotoxemia did not impair cholinergic responsiveness in diabetic atria. These findings corroborates with development of endotoxin tolerance in diabetic rats.