AUTONOMIC NERVOUS FUNCTION IN MICE AND VOLES (MICROTUS-ARVALIS) - INVESTIGATION BY POWER SPECTRAL-ANALYSIS OF HEART-RATE-VARIABILITY

We have studied the autonomic nervous function in voles (Microtus arva lis) and mice. For this purpose, ECGs were recorded from conscious and unrestrained voles and mice using radiotelemetry and the autonomic ne rvous function was investigated by the power spectral analysis of hear t rate variability. Heart rate in voles was lower than mice and the co efficient of variance was larger in voles. In the power spectra of vol es and mice, there were two major spectral components with the high fr equency (HF) peak generally appearing between 2.0 and 4.0 Hz, and the low frequency (LF) peak appearing below 0.6 Hz. On the basis of this d ata, we set the two frequency bands as LF (0.1-1.0 Hz) and HF (1.0-5.0 Hz) to evaluate autonomic nervous function. The LF and HF powers were larger in voles than mice. The LF/HF ratio was thought to provide a c onvenient index of autonomic nervous balance and was smaller in voles than mice. The LF powers in both species were reduced by atropine, but propranolol reduced the LF power only in mice. The HF power was reduc ed by atropine only in voles. The intrinsic heart rate produced by a d ouble blockade with atropine and propranolol in voles was almost the s ame as control levels, but in mice was lower than controls. The ratio of the LF and HF powers by a double blockade were almost the same as t hose of the administration of atropine in voles, but nearer to propran olol in mice. These results suggested that the parasympathetic nervous function was predominant in voles, but the sympathetic one was predom inant in mice.