Relationship between cortical electrical and cardiac autonomic activities in the awake lizard,Gallotia galloti

Abstract

ECG and EEG signals were simultaneously recorded in lizards, Gallotia galloti, both in control conditions and under autonomic nervous system (ANS) blockade, in order to evaluate possible relationships between the ANS control of heart rate and the integrated central nervous system activity in reptiles. The ANS blockers used were prazosin, propranolol, and atropine. Time-domain summary statistics were derived from the series of consecutive R-R intervals (RRI) of the ECG to measure beat-to-beat heart rate variability (HRV), and spectral analysis techniques were applied to the EEG activity to assess its frequency content. Both prazosin and atropine did not alter the power spectral density (PSD) of the EEG low frequency (LF: 0.5-7.5 Hz) and high frequency (HF: 7.6-30 Hz) bands, whereas propranolol decreased the PSD in these bands. These findings suggest that central β-adrenergic receptor mechanisms could mediate the reptilian waking EEG activity without taking part any α 1 -adrenergic and/or cholinergic receptor systems. In 55% of the lizards in control conditions, and in ~43% of the lizards under prazosin and atropine, a negative correlation between the coefficient of variation of the series of RRI value (CV RRI ) and the mean power frequency (MPF) of the EEG spectra was found, but not under propranolol. Consequently, the lizards' HRV-EEG-activity relationship appears to be independent of α 1 -adrenergic and cholinergic receptor systems and mediated by β-adrenergic receptor mechanisms.

Alterations in the coupling functions between cortical and cardio-respiratory oscillations due to anaesthesia with propofol and sevoflurane

“…While interactions have already been studied in lizards [ 52 ], mice [ 53 ], rats [ 15 ] and dogs [ 54 ], here we report the first insights into cardio-respiratory-cortical interactions in humans, in both the awake and anaesthetized states. Moreover, our extension of cross-frequency coupling to include the analysis of coupling functions has allowed us to investigate the interactions in greater depth by introducing the notion of the functional form , which represents a new dimension in the analysis of neuronal effective interactions.…”

Electrocardiographic Parameters in the Gomeran Giant Lizard, Gallotia bravoana

“…To date, the reptilian electrocardiogram (EC G ) has been used as a diagnostic tool in cases o f clinical cardiac disease and fo r m o n ito rin g a n a e sth e sia (C o o k & W estrom , 1979, A nderson, et al, 1999). H ow ever, its use is lim ited by the paucity o f clinically relevant published m aterial on the sub j e c t. To th e a u t h o r s ' k n o w le d g e , E C G h a s b e e n fu lly described in only a few squam ata including g reen iguana, Iguana iguana, (Albert, et al, 1999) brow n tree snake, Boiga irregularis, (Anderson, et al, 1999), rat snake, Elaphe obsoleta, (Jacob and M cD onald, 1975), carp et p y th o n , M orelia sp ilo ta va riegata, (R is h n iw an d C a rm e l, 1 9 9 9 ), In d ia n python, Python molurus, (Snyder, et al, 1999) and G allot's lizard, Gallotia galloti (de Vera and G onzalez, 1999, de Vera, et al, 2000). This report describes the E C G o f the G om eran giant lizard, Gallotia bravoana.…”

Control of heart rate during thermoregulation in the heliothermic lizard Pogona barbata: importance of cholinergic and adrenergic mechanisms

“…There is evidence that changes in the cholinergic tone on the heart are the principle mechanism controlling heart rate during exercise in fish (Axelsson et al, 1987;Altimiras et al, 1997). In contrast, heart rate variability in a lizard (Gallotia galloti) appeared to be mediated primarily by β-adrenergic receptor mechanisms (DeVera et al, 2000). Moreover, there are species-specific differences in the relative importance of cholinergic and adrenergic autonomic control of the heart.…”