Binding of the non-peptide vasopressin V1a receptor antagonist SR-49059 in the rat brain: an in vitro and in vivo autoradiographic study

The role of the sympathetic limb of the autonomic nervous system (ANS) in the mediation of oscillations in consecutive beat-to-beat RR interval (RRI) and systolic blood pressure (SBP) values of lizards, Gallotia galloti, was investigated using spectral analysis and measuring effects of autonomic blockers. alpha-Adrenergic blockade decreased the power spectral density (PSD) of both RRI and SBP very low frequency (VLF: 0.007-0.055 Hz) and low frequency (LF: 0.055-0.150 Hz) bands, whereas beta-adrenergic blockade increased the PSD of both RRI- and SBP-VLF and RRI- and SBP-LF bands. These findings suggest that in lizards 1) the VLF and LF peaks of RRI and SBP power spectra are alpha-adrenergic mediated, and that 2) the beta-adrenergic activity of the sympathetic system may act buffering all RRI and SBP oscillations below 0.150 Hz. These results, when analyzed jointly with the ones obtained from a previous study (De Vera and González. 1997. Comp Biochem Physiol 85A:389-394) on the effects of parasympathetic blockade on lizards' RRI and SBP oscillations, demonstrate that these reptiles, like mammals, exhibit spontaneous short-term oscillations in their HR and SBP which are mediated by the ANS. However, unlike mammals, the RRI and ABP low-frequency oscillations in Gallotia seem to be similarly affected by the ANS and appear to be powered by alpha-adrenergic and parasympathetic activities and buffered by beta-adrenergic activity.