Regulation of heart rate variation by the autonomic nervous system in neonatal lambs.

We studied the role of the autonomic nervous system in the regulation of heart rate variation (HRV) in 12 chronically instrumented neonatal lambs. HRV was quantified from ECG tracings by computing periodic HRV distributions at frequencies of 0.02-1.

Heart rate variation in relation to age and sleep state in neonatal lambs.

The heart rate (HR), heart rate variation (HRV) and the power spectrum of the HR were studied in 1 to 10-week-old neonatal lambs. The average HR was highest and the indices of the HRV were lowest at the age of 1 to 3 weeks. However, there was a decreasing trend in the overall HRV with advancing age when it was normalized in relation to the average HR.

Suppression of postganglionic sympathetic discharges by pentobarbital in endotoxic cats.

Pentobarbital (7-9 mg/kg) profoundly suppressed the sympathetic postganglionic cardiac and splenic discharges in endotoxic cats under chloralose anesthesia. Concurrently, the pre-existent tachycardia was replaced by bradycardia, and the blood pressure fell further. The findings are interpreted to imply a pentobarbital-induced sympatholysis.

Distension of pulmonary vein--left atrial junction: heart rate responses in conscious and anesthetized dogs.

The cardiac chronotropic effects of distension of pulmonary vein-left atrial junction were investigated in conscious dogs and in dogs anesthetized with intravenous alpha-chloralose (100 mg/kg) or pentobarbital (30 mg/kg). All the experiments were made on trained, chronically instrumented, closed chest animals held in horizontal position. Inflation of a single small balloon in the junction elicited a tachycardic response both in conscious and chloralose-anesthetized dogs, while in pentobarbital anesthesia no change in heart rate was found.

Suppresion of autonomic postganglionic discharges by pentobarbital in dogs, with or without endotoxemia.

Initial effects of pentobarbital (8 mg/kg) on autonomic efferent and afferent discharge rates were studied in 26 dogs under morphine-chloralose anesthesia. Half of the dogs were given endotoxin E. coli (1 mg/kg) before pentobarbital.