Power spectra of the inter-cycle heart fluctuations in Xenopus laevis (L.), conscious or pithed, exposed to temperature changes and pharmacological treatments]

Spectral analysis of spontaneous heart rate fluctuations, a powerful noninvasive tool for quantifying autonomic nervous system activity, was assessed in Xenopus Laevis, intact or spinalized, at different temperatures and by use of pharmacological tools. As expected, increasing the body temperature resulted in a positive chronotropic effect, both in the conscious and the spinalized preparations. Characteristic modifications of the spontaneous heart rate fluctuations were detected in both the experimental conditions. Different receptor drugs, which selectively interfere with the variously superimposed vegetative sections of the nervous control, had been proved to be effective in the new assay.