Correlation between maternal and fetal heart rate increases with fetal mouse age in typical development and is disturbed in autism mouse model treated with valproic acid.

Introduction: Autism spectrum disorder (ASD) is considered a significant behavioral problem that is characterized by impairment in social interaction and communication. It is believed that some cases of ASD originate in the intrauterine maternal environment. Therefore, we hypothesized that there might be qualitative changes in the interaction between the mother and fetus in ASD during the prenatal period, hence, we investigated the similarity patterns between maternal and fetal heart rate (HR). Methods: In this study, we first demonstrate the presence and formation of similarities between maternal and fetal RR interval (RRI) collected from typical developmental mice at different embryonic days (EDs), ED13.5, ED15.5, ED17.5, and ED18.5. The similarities were quantified by means of cross-correlation (CC) and magnitude-squared coherence (MSC) analyses. Correlation analysis between the CC coefficients and EDs and between MSC coefficients and EDs showed that the same coefficients increase with EDs, suggesting that similarities between maternal and fetal RRI are associated with typical fetal development. Next, because maternal and fetal similarities were indicative of development, a comparison analysis between the autism mouse model (injected with valproic acid (VPA)), and the control group (injected with saline) was performed for ED15.5 and ED18.5. Results: The results of the comparison showed that the CC and MSC coefficients of VPA fetuses were significantly lower than that of the control group. The lower coefficients in VPA-treated mice suggest that they could be one of the features of ASD symptoms. The findings of this study can assist in identifying potential ASD causes during the prenatal period.

Effect of Valproic Acid on Maternal - Fetal Heart Rates and Coupling in Mice on Embryonic day 15.5 (E15.5).

Prenatal uptake of valproic acid (VPA) was associated with increased risk of fetal cardiac anomalies and autism spectrum disorder (ASD), but uptake of VPA is considered the only effective treatment for epilepsy and other neurological disorders. Up until now, little is known about the effect of VPA on maternal - fetal heart rate (HR) coupling patterns; therefore, this study aims at studying such patterns in mice on embryonic day 15.5 (E15.5). At E12.5, 8 mothers were injected with VPA (VPA group) and another 8 mothers were injected with saline (control group). At E15.5, electrocardiogram (ECG) records of 15 minutes were collected from the 16 mothers and 25 fetuses. A maximum of 5-minutes and a minimum of 1-minute were selected from the ECG data for analysis. Mean RR intervals and coupling ratios and their occurrence percentages were calculated per 1minute. 1-minute analysis was done for periods with no arrhythmia and clear R peaks. The total number of 1-minute segments that were analyzed was 56 for the saline group and 54 for the VPA group. The correlation analysis between the 1:3 and 2:6 coupling ratios and RR intervals revealed that the ratios were significantly correlated in the saline group, whereas no significant correlations were observed in the VPA group. The results further revealed that fetal RR intervals are strongly correlated with maternal RR intervals in the saline group, but the same correlation is different in the VPA group. The presented results imply that maintaining certain coupling patterns are important for proper fetal cardiac development and maternal uptake of VPA may affect maternal-fetal HRs interactions.

Alterations in the autonomic nerve activities of prenatal autism model mice treated with valproic acid at different developmental stages.

Autism spectrum disorder (ASD) is characterized by impairment of social communication, repetitive behavior and restrictive interest. The risk of ASD is strongly associated with the prenatal period; for instance, the administration of valproic acid (VPA) to pregnant mothers increases risk of ASD in the child. Patients with ASD often exhibit an alteration in the autonomic nervous system. In this study, we assessed the autonomic nervous activity at each prenatal developmental stage of model mice of ASD treated with VPA, to clarify the relationship between timing of exposure and ASD symptoms. The assessment of the autonomic nervous activity was performed based on the analysis of electrocardiography data collected from fetal and adult mice. Interestingly, VPA model mouse fetuses exhibited a significantly lower activity of the sympathetic nervous system. In contrast, sympathetic nervous activity at P0 was significantly higher. In adult VPA model mice, the parasympathetic activity of female VPA mice was suppressed. Moreover, female VPA mice showed reduced the parasympathetic activity after exposure to restraint stress. These results suggest that the autonomic nervous activity of VPA model mice was altered from the fetal stage, and that the assessment of autonomic nervous activities at an early developmental stage could be useful for the understanding of ASD.

Effect of ß-blocker on maternal-fetal heart rates and coupling in pregnant mice and fetuses.

The aim of this preliminary study is to look how maternal-fetal heart rates and their coupling patterns are influenced by injection of ß blocker(propranolol) into pregnant mice. Total of 6 pregnant female mice were divided into two groups [control (N=3) and ß blockade (N=3)]. On 17.5-day mean heart rate of mothers and fetuses (MHR and FHR) were simultaneously measured for 20 minutes (10 minutes under normal condition and 10 minutes with saline (to control group) and propranolol (to the ß blockade group) solution by using an invasive maternal and fetal electrocardiogram techniques with needle electrodes. Results show that FHR decreased and maternal-fetal heart rate coupling (λ) patterns changed with propranolol infusion (no change with saline). Statistical test showed that changes (increase/decrease from pre to post values) in mean, rmssd and power spectral density (PSD) (2~4 Hz)) of MHR, short term variability of FHR, PSD (0.0~1.0 Hz) of FHR and λ were found to be significantly associated with treatment types (saline to propranolol). The presented results and protocol allow for assessment of ß adrenergic control of maternal and fetal heart, which will further enhance the value of the mouse as a model of heritable human pregnancy and hypertension.

Regulation of maternal-fetal heart rates and coupling in mice fetuses.

The aim of this preliminary study is to investigate if there is any evidence of maternal-fetal heart rate coupling in mice fetuses and how the coupling patterns are regulated by vagal nervous system on beat by beat. Total of 6 pregnant female mice were divided into two groups [control (N=3) and vagal blockade (N=3)]. On 17.5-day beat-to-beat heart rates of mothers and fetuses (MHR and FHR) were simultaneously measured for 20 minutes (10 minutes under normal condition and 10 minutes with saline (to control group) and atropine (to the vagal blockade group)) solution by using an invasive maternal and fetal electrocardiogram techniques with needle electrodes. Results show that occasional strong maternal-fetal heart rate coupling (strength was measured by $\lambda$) appeared and its patterns changed with atropine infusion (no change with saline). Additionally, fisher's exact test shows that changes (increase/decrease from pre to post injection values) in mean, rmssd and power spectral density (PSD) (2~4 Hz) of MHR, rmssd FHR and PSD (2~4 Hz) of${\lambda }$were found to be significantly (p<0.05) associated with treatment types (saline/ atropine). The presented results and protocol allow for the first time in the assessment of autonomic regulation of maternal and fetal heart and their interactions, which will further enhance the value of the mouse as a murine model of heritable human pregnancy and perinatal complications due to maternal conditions.