Behavioural, endocrine and cardiac autonomic responses to a model of startle in horses

Startle is a fast response elicited by sudden acoustic, tactile or visual stimuli in a variety of animal species and in humans. The magnitude of startle response can be modulated by external and internal variables and can be a useful tool to study the sensory-motor integration in animals. Different stimuli have been used to induce startle in horses, which makes it difficult to compare the responses to these different approaches. The present study uses ultra-short-term heart rate variability (HRV) analysis to characterize the cardiac autonomic modulation, reactivity assessment and blood cortisol measurements to describe the behavioural and endocrine responses to a simple, easy to replicate, effective and safe method of startle (an umbrella is abruptly opened near the horse). The ultra-short-term (64 s) heart rate (HR) series were interpolated (4 Hz) and divided into 256 points segments then the spectra calculated (Fast Fourier Transform). The spectra were then integrated into low (LF; 0.01–0.07 Hz; Index of Cardiac Sympathetic Modulation) and high (HF; 0.07–0.50 Hz; Index of Cardiac Parasympathetic Modulation) frequency bands. Following the startle test, the HR (p = 0.0101), the power of the LF band of the cardiac interval spectrum (p = 0.0002) and the LF/HF ratio (p = 0.0066) were found to be higher, whereas the power of the HF band of the cardiac interval spectrum was found to be lower (p = 0.0002). Also, the horses showed a noticeable escape response, with latency of reaction varying from 0.28 to 1.28 s, duration of reaction ranging from 1.52 to 7.92 s and escape distance covered varying from 3.43 to 9.97 m. However, the endocrine measurements failed to reveal significant changes in the cortisol levels after the startle test. We conclude that the startle test used in the current study was effective to produce changes in behavioural parameters and cardiac autonomic modulation of the horses and can therefore be an appropriate tool for neurobiological studies. Furthermore, the use of ultra-short segments (64 s) for HRV analysis appears to be effective and promising for the detection of mental stress in horses.Instituto de Genética Veterinari

Behavioural, endocrine and cardiac autonomic responses to a model of startle in horses

Startle is a fast response elicited by sudden acoustic, tactile or visual stimuli in a variety of animal species and in humans. The magnitude of startle response can be modulated by external and internal variables and can be a useful tool to study the sensory-motor integration in animals. Different stimuli have been used to induce startle in horses, which makes it difficult to compare the responses to these different approaches. The present study uses ultra-short-term heart rate variability (HRV) analysis to characterize the cardiac autonomic modulation, reactivity assessment and blood cortisol measurements to describe the behavioural and endocrine responses to a simple, easy to replicate, effective and safe method of startle (an umbrella is abruptly opened near the horse). The ultra-short-term (64. s) heart rate (HR) series were interpolated (4. Hz) and divided into 256 points segments then the spectra calculated (Fast Fourier Transform). The spectra were then integrated into low (LF; 0.01-0.07. Hz; Index of Cardiac Sympathetic Modulation) and high (HF; 0.07-0.50. Hz; Index of Cardiac Parasympathetic Modulation) frequency bands. Following the startle test, the HR (p = 0.0101), the power of the LF band of the cardiac interval spectrum (p = 0.0002) and the LF/HF ratio (p = 0.0066) were found to be higher, whereas the power of the HF band of the cardiac interval spectrum was found to be lower (p = 0.0002). Also, the horses showed a noticeable escape response, with latency of reaction varying from 0.28 to 1.28. s, duration of reaction ranging from 1.52 to 7.92. s and escape distance covered varying from 3.43 to 9.97. m. However, the endocrine measurements failed to reveal significant changes in the cortisol levels after the startle test. We conclude that the startle test used in the current study was effective to produce changes in behavioural parameters and cardiac autonomic modulation of the horses and can therefore be an appropriate tool for neurobiological studies. Furthermore, the use of ultra-short segments (64 s) for HRV analysis appears to be effective and promising for the detection of mental stress in horses.Fil: Villas Boas, Julia Dias. Universidade Federal do Estado do Rio de Janeiro; BrasilFil: Martins Dias, Daniel Penteado. Universidade de Sao Paulo; BrasilFil: Trigo, Pablo Ignacio. Universidade Federal do Estado do Rio de Janeiro; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: dos Santos Almeida, Norma Aparecida. Universidade Federal do Estado do Rio de Janeiro; BrasilFil: de Almeida, Fernando Queiroz. Universidade Federal do Estado do Rio de Janeiro; BrasilFil: de Madeiros, Magda Alves. Universidade Federal do Estado do Rio de Janeiro; Brasi

Acupuncture affects autonomic and endocrine but not behavioural responses induced by startle in horses

Startle is a fast response elicited by sudden acoustic, tactile, or visual stimuli in a variety of animals and in humans. As the magnitude of startle response can be modulated by external and internal variables, it can be a useful tool to study reaction to stress. Our study evaluated whether acupuncture can change cardiac autonomic modulation (heart rate variability); and behavioural (reactivity) and endocrine (cortisol levels) parameters in response to startle. Brazilian Sport horses (n = 6) were subjected to a model of startle in which an umbrella was abruptly opened near the horse. Before startle, the horses were subjected to a 20-minute session of acupuncture in acupoints GV1, HT7, GV20, and BL52 (ACUP) and in nonpoints (NP) or left undisturbed (CTL). For analysis of the heart rate variability, ultrashort-term (64 s) heart rate series were interpolated (4 Hz) and divided into 256-point segments and the spectra integrated into low (LF; 0.01–0.07 Hz; index of sympathetic modulation) and high (HF; 0.07–0.50 Hz; index of parasympathetic modulation) frequency bands. Acupuncture (ACUP) changed the sympathovagal balance with a shift towards parasympathetic modulation, reducing the prompt startle-induced increase in LF/HF and reducing cortisol levels 30 min after startle. However, acupuncture elicited no changes in behavioural parameters.Instituto de Genética Veterinari

Los efectos de la estimulación eléctrica transcutánea del diafragma en el balance autónomo cardiaco en individuos sanos: estudio clínico aleatorio

La estimulación eléctrica transcutánea del diafragma (EETD) es un método que moviliza la musculatura respiratoria que interfiere en el patrón y en la frecuencia respiratoria. Para evaluar las alteraciones en el balance autónomo cardiaco por la EETD en individuos sanos, se empleó un modelo prestablecido de estimulación eléctrica muscular del diagrama. Han participado 22 voluntarios con edad entre 22 y 35 años, sin enfermedades cardiacas, puestos en grupos aleatorios: Grupo control (n=8) y EETD (n=14). Se aplicó el protocolo de estimulación eléctrica en individuos en posición decúbito supino. Al grupo control se lo sometió a la estimulación eléctrica a nivel perceptual, mientras que en el EETD la estimulación le generaba contracción del diafragma. Los intervalos cardiacos (CI) se registraron a través del monitor de ritmo cardiaco polar (RS800CX). Se estudió la variabilidad del intervalo cardiaco en los dominios tiempo y frecuencia. En el grupo control, la estimulación eléctrica no presentó alteraciones en la duración del intervalo cardiaco y su variabilidad (CI: 761±44 vs. 807±39ms; RMSSD: 37±9 vs. 42±13ms; LF: 69±6 vs. 67±5nu; HF: 31±6 vs. 33±5nu; comparado con las condiciones de base). Pero si comparado las condiciones de base en el grupo EETD presentó una disminución en la modulación simpática cardiaca (LF: 43±3 vs. 63±4nu) y un aumento en la modulación parasimpática cardiaca (RMSSD: 109±10 vs. 41±6ms; HF: 57±3 vs. 37±4nu) durante la realización de este método. Sin embargo, la duración del intervalo cardiaco no presentó alteraciones por la estimulación eléctrica del diafragma (CI: 686±59 vs. 780±31ms). Se puede concluir que el empleo de la EETD promueve cambios significativos en el balance simpático, resultando en una modulación parasimpática cardiaca más grande, posiblemente inducida del aumento de la movilidad del diafragma.The transcutaneous electrical diaphragmatic stimulation (TEDS) is a technique of respiratory muscle activation that affects breathing pattern and rhythm. In an attempt to evaluate changes in cardiac autonomic balance in response to TEDS in healthy individuals, we used a well-established TEDS model. Twenty-two volunteers aged between 22 and 35 years old, with no cardiac pathology history, were randomized into two groups (control, n = 8; TEDS, n = 14). The individuals were allowed to rest in supine position and were then subjected to the electrical stimulation protocol. The control group was subjected to electrical stimulation at perceptive level, whereas for the TEDS group the electric stimulus generated diaphragm contraction. Cardiac intervals (CI) were sampled by a Polar RS800CX monitor. Cardiac interval variability was studied in the time and frequency domains. In the control group, electrical stimulation did not change cardiac interval length and variability (CI: 761±44 vs. 807±39 ms; RMSSD: 37±9 vs. 42±13 ms ; LF: 69±6 vs. 67±5 nu; HF: 31±6 vs. 33±5 nu; all comparisons versus baseline). Nevertheless, as compared to baseline, TEDS group showed decreased sympathetic cardiac modulation (LF: 43±3 vs. 63±4 nu) and increased parasympathetic cardiac modulation (RMSSD: 109±10 vs. 41±6 ms; HF: 57±3 vs. 37±4 nu) during diaphragmatic stimulation. However, cardiac interval length was not changed by electrical stimulation (CI: 686±59 vs. 780±31 ms). It can be suggested that the use of TEDS stimulus leads to pronounced changes in the cardiac sympathovagal balance, with higher parasympathetic cardiac modulation, possibly induced by increased diaphragmatic excursion.A estimulação diafragmática elétrica transcutânea (EDET) é uma técnica de mobilização da musculatura respiratória que interfere no padrão e no ritmo respiratório. Na tentativa de avaliar as alterações no balanço autonômico cardíaco à EDET em indivíduos saudáveis, foi utilizado um modelo já estabelecido de eletroestimulação diafragmática. 22 voluntários com idades entre 22 e 35 anos, sem histórico cardíaco, foram randomizados em dois grupos (controle, n=8; EDET, n=14). O protocolo de eletroestimulação foi aplicado nos indivíduos em repouso (posição supina). O grupo controle foi submetido a estimulação elétrica em nível perceptivo, enquanto no grupo EDET o estímulo gerava contração diafragmática. Os intervalos cardíacos (CI) foram registrados por cardiofrequencímetro Polar (RS800CX). A variabilidade do intervalo cardíaco foi estudada nos domínios de tempo e frequência. No grupo controle, a estimulação elétrica não alterou a duração do intervalo cardíaco e sua variabilidade (CI: 761±44 vs. 807±39ms; RMSSD: 37±9 vs. 42±13ms; LF: 69±6 vs. 67±5nu; HF: 31±6 vs. 33±5nu), em comparação às condições basais). No entanto, o grupo EDET apresentou diminuição na modulação simpática cardíaca (LF: 43 ±3 vs. 63±4nu) e aumento da modulação parassimpática cardíaca (RMSSD: 109±10 vs. 41±6ms; HF: 57±3 vs. 37±4nu) durante a eletroestimulação diafragmática. No entanto, a duração do intervalo cardíaco não foi alterada por estimulação elétrica (CI: 686±59 vs. 780±31ms). Pode-se sugerir que o uso da EDET promove mudanças acentuadas no balanço simpatovagal, resultando em maior modulação parassimpática cardíaca, possivelmente induzida pelo aumento da mobilidade diafragmática

Revisiting the Sequence Method for Baroreflex Analysis

The sequence method is an important approach to assess the baroreflex function, mainly because it is based on the spontaneous fluctuations of beat-by-beat arterial pressure (for example, systolic arterial pressure or SAP) and pulse interval (PI). However, some studies revealed that the baroreflex effectiveness index (BEI), calculated through the sequence method, shows an intriguing oscillatory pattern as function of the delay between SAP and PI. It has been hypothesized that this pattern is related to the respiratory influence on SAP and/or PI variability, limiting the SAP ramps to 3 or 4 beats of length. In this study, this hypothesis was tested by assessing the sequence method using raw (original) and filtered series. Results were contrasted to the well-established transfer function, estimated between SAP and PI. Continuous arterial pressure recordings were obtained from healthy rats (N = 61) and beat-by-beat series of SAP and PI were generated. Low-pass (LP) and high-pass (HP) filtered series of SAP and PI were created by filtering the original series with a cutoff frequency of 0.8 Hz. Original series were analyzed by either the sequence method or cross-spectral analysis (transfer function) at low- (LF) and high- (HF) frequency bands, while filtered series were evaluated only by the sequence method. Baroreflex sensitivity (BRS) and BEI of original series, calculated by sequence method, was highly (85–90%) determined by HP series, with no significant association between original and LP series. A high correlation (>0.7) was found between the BRS estimated from original series (sequence method) and HF band (transfer function), as well as for LP series (sequence method) and LF band (transfer function). These findings confirmed the hypothesis that the sequence method quantifies only the high-frequency components of the baroreflex, neglecting the low-frequency influences, such as the Mayer waves. Therefore, we propose using both the original and LP filtered time series for a broader assessment of the baroreflex function using the sequence method

RESPOSTAS ELETROCARDIOGRÁFICAS DE EQUINOS AO TREINAMENTO COM BASE NA CURVA VELOCIDADE-LACTATO DETERMINADA EM ESTEIRA ROLANTE

Neste trabalho, avaliaram-se, mediante exame eletrocardiográfico, as adaptações cardiovasculares de equinos ao treinamento com base na curva velocidade-lactato. Para tanto, foram utilizados oito equinos da raça Puro Sangue Árabe previamente submetidos a um período de quatro meses de destreinamento. Os animais realizaram inicialmente um teste de esforço progressivo (ET), durante o qual colheram-se amostras de sangue para determinação do lactato. A velocidade na qual a concentração de lactato atingiu 4,0 mmol/L (V4) foi calculada por meio de análise de regressão. Utilizaram-se 60% de V4 como velocidade de treinamento em esteira rolante, com duração de 45 minutos, três vezes por semana em dias alternados, durante oito semanas. Exames eletrocardiográficos (ECG) foram realizados antes e após o período de treinamento. O treinamento melhorou o condicionamento físico dos equinos, confirmado pelo aumento tanto de V2 como de V4 no segundo ET. Pelo exame ECG, observou-se aumento significativo na amplitude de onda R após o treinamento. Em que pese o treinamento ter melhorado a atividade metabólica, não foi suficiente para conferir modificações em parâmetros cardíacos, embora tenha promovido discretas mudanças no exame eletrocardiográfico. PALAVRAS-CHAVES: Adaptações ao treinamento, cardiovascular, eletrocardiografia, esteira, equino.

Investigating autonomic nervous system dysfunction among patients with post-COVID condition and prolonged cardiovascular symptoms

Heart Rate Variability (HRV) and arterial pressure (AP) variability and their responses to head-up tilt test (HUTT) were investigated in Post-COVID-19 syndrome (PCS) patients reporting tachycardia and/or postural hypotension. Besides tachycardia, PCS patients also showed attenuation of the following HRV parameters: RMSSD [square root of the mean of the sum of the squares of differences between adjacent normal-to-normal (NN) intervals] from statistical measures; the power of RR (beat-to-beat interval) spectra at HF (high frequency) from the linear method spectral analysis; occurrence of 2UV (two unlike variation) pattern of RR from the nonlinear method symbolic analysis; and the new family of statistics named sample entropy, when compared to control subjects. Basal AP and LF (low frequency) power of systolic AP were similar between PCS patients and control subjects, while 0 V (zero variation) patterns of AP from the nonlinear method symbolic analysis were exacerbated in PCS patients. Despite tachycardia and a decrease in RMSSD, no parameter of HRV changed during HUTT in PCS patients compared to control subjects. PCS patients reassessed after 6 months showed higher HF power of RR spectra and a higher percentage of 2UV pattern of RR. Moreover, the reassessed PCS patients showed a lower occurrence of 0 V patterns of AP, while the HUTT elicited HR (heart rate) and AP responses identical to control subjects. The HRV and AP variability suggest an autonomic dysfunction with sympathetic predominance in PCS patients. In contrast, the lack of responses of HRV and AP variability indices during HUTT indicates a marked impairment of autonomic control. Of note, the reassessment of PCS patients showed that the noxious effect of COVID-19 on autonomic control tended to fade over time

Induction of chronic non-inflammatory widespread pain increases cardiac sympathetic modulation in rats

Fibromyalgia (FM) is characterized by chronic non-inflammatory widespread pain (CWP) and changes in sympathetic function. In attempt to elucidate the pathophysiological mechanisms of FM we used a well-established CWP animal model. We aimed to evaluate changes in cardiac autonomic balance and baroreflex function in response to CWP induction in rats. CWP was induced by two injections of acidic saline (pH 4.0, n = 8) five days apart into the left gastrocnemius muscle. Control animals were injected twice with normal saline (pH 7.2, n = 6). One day after the second injection of acidic saline or normal saline, the animals had pulse interval (PI) and systolic arterial pressure (SAP) variability, and spontaneous baroreflex sensitivity (BRS) evaluated. After induction of CWP, there was an increase of power in the low frequency (LF) band of PI spectrum (12.75 +/- 1.04 nu), a decrease in the high frequency (HF) band (87.25 +/- 1.04 nu) and an increase of LF/HF ratio (0.16 +/- 0.01), when compared to control animals (7.83 +/- 1.13 nu LF; 92.16 +/- 1.13 nu HF; 0.08 +/- 0.01 LF/HF). In addition, there was an increase of power in the LF band of SAP spectrum (7.93 +/- 1.39 mmHg(2)) when compared to control animals (2.97 +/- 0.61 mmHg(2)). BRS was lower in acidic saline injected rats (0.59 +/- 0.06 ms/mmHg) when compared to control animals (0.71 +/- 0.03 ms/mmHg). Our results showed that induction of CWP in rats shifts cardiac sympathovagal balance towards sympathetic predominance and decreases BRS. These data corroborate findings in humans with FM. (C) 2011 Elsevier B.V. All rights reserved