Oxytocin's role on the cardiorespiratory activity of endotoxemic rats

BACKGROUND

Recent findings concerning oxytocin indicate its anti-inflammatory, cardioprotective and parasympathetic modulating properties. In this study, we investigated the effects of systemically applied oxytocin on the cardiorespiratory activity in a rodent model of moderate endotoxemia.

METHODS

Telemetrically recorded electrocardiogram (ECGs) from animals which received lipopolysaccharide (LPS); oxytocin (Ox); lipopolysaccharide+oxytocin (LPS+Ox), or vehicle (V) were analyzed using the ECG-derived respiration (EDR) technique to estimate the respiratory rate. The mean R-R interval and the spectral parameters of heart rate variability (HRV), such as the natural logarithm of the high frequency (lnHF) and low frequency (lnLF) components were also estimated up to 24h after treatment.

RESULTS

The endotoxemic animals (LPS) showed an elevated respiratory rate as well as a reduced mean R-R interval, lnHF and lnLF components compared to controls (V) from +5 to +12h after the treatment. The administration of oxytocin significantly attenuated the hyperventilation produced by the LPS-induced endotoxemia (LPS+Ox) and restored the values of the mean R-R interval and such spectral parameters at different time points.

CONCLUSIONS

Our results support the existence of a link among the respiratory, cardiovascular, and immune systems in which oxytocin seems to act as a potential cardioprotective peptide by favoring cardiac cholinergic autonomic coupling. As a result, oxytocin diminished animal's endotoxemic tachypnea and restored the cardiorespiratory interactions, which was indicated by the spectral components of HRV.

A comparison of heart rate variability in women at the third trimester of pregnancy and during low-risk labour

Heart rate variability (HRV) has been recognised as a non-invasive method for assessing cardiac autonomic regulation. Aiming to characterize HRV changes at labour in women, we studied 10 minute ECG recordings from young mothers (n=30) at the third trimester of pregnancy (P) or during augmentation of labour (L) (n=30). Data of the L group were collected when no-contractions (L-NC) or the contractile activity (L-C) was manifested. Accordingly, the inter-beat interval (IBI) time series were processed to estimate relevant parameters of HRV such as the mean IBI (IBI¯), the mean heart rate HR¯, the root mean square of successive differences (RMSSD) in IBIs, the natural logarithm of high-frequency component (LnHF), the short-term scaling parameters from detrended fluctuation and magnitude and sign analyses such as (α1, α1(MAG), α1(SIGN)), and the sample entropy (SampEn). We found statistical differences (p<0.05) for RMSSD among P and L-NC/L-C groups (25 ± 13 vs. 36 ± 14/34 ± 16 ms) and for LnHF between P and L-NC (5.37 ± 1.15 vs. 6.05 ± 0.86 ms(2)). Likewise, we identified statistical differences (p<0.05) for α1(SIGN) among P and L-NC/L-C groups (0.19 ± 0.20 vs. 0.32 ± 0.17/0.39 ± 0.13). By contrast, L-NC and L-C groups showed statistical differences (p<0.05) in α1(MAG) (0.67 ± 0.12 vs. 0.79 ± 0.12), and SampEn (1.62 ± 0.26 vs. 1.20 ± 0.44). These results suggest that during labour, despite preserving a concomitant non-linear influence, the maternal short-term cardiac autonomic regulation becomes weakly anticorrelated (as indicated by α1(SIGN)); furthermore, an increased vagally mediated activity is observed (as indicated by RMSSD and LnHF), which may reflect a cholinergic pathway activation owing to the use of oxytocin or the anti-inflammatory cholinergic response triggered during labour.