Inspiratory modulation of sympathetic activity is increased in female rats exposed to chronic intermittent hypoxia

Souza, George M. P. R.; Bonagamba, Leni Gomes Heck; Amorim, Margarete Cristiane de Costa Trindade; Moraes, Davi J. A.; Machado, Benedito H.

doi:10.1113/ep085850

Cited by 24 publications

(38 citation statements)

References 42 publications

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“…; Souza et al . ). In the present study, the levels of sympathetic outflow during the three respiratory phases of the respiratory cycle were normal in SAD compared with Sham rats.…”

Section: Discussionmentioning

confidence: 97%

“…; Souza et al . ), indicating a coupling between the respiratory and the sympathetic neural circuits. The interaction between respiratory and sympathetic networks is different in each experimental model of neurogenic hypertension, resulting in sympathetic overactivity in different phases of the respiratory cycle (Czyżyk‐Krzeska & Trzebski, ; Zoccal et al .…”

Section: Discussionmentioning

confidence: 98%

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Changes in the inspiratory pattern contribute to modulate the sympathetic activity in sino‐aortic denervated rats

Amorim

Bonagamba

Souza

et al. 2017

Experimental Physiology

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What is the central question of this study? Sino-aortic denervated (SAD) rats present normal levels of sympathetic activity and mean arterial pressure. However, neural mechanisms regulating the sympathetic activity in the absence of arterial baroreceptors remain unclear. Considering that respiration modulates the sympathetic activity, we hypothesize that changes in the respiratory network contribute to keep the sympathetic outflow in the normal range after removal of arterial baroreceptors. What is the main finding and its importance? Despite longer inspiration observed in SAD rats, the respiratory-sympathetic coupling is working within a normal range of variation. These findings suggest that in the absence of arterial baroreceptors the respiratory modulation of sympathetic activity is maintained within the normal range. The activity of presympathetic neurons is under respiratory modulation, and changes in the central respiratory network may impact on the baseline sympathetic activity and mean arterial pressure. It is well known that after removal of baroreceptor afferents [sino-aortic denervation (SAD)], rats present an unexpected normal level of mean arterial pressure. We hypothesized that changes in the respiratory pattern and in the respiratory modulation of the sympathetic activity contribute to keep the sympathetic outflow within a normal range of variation in the absence of arterial baroreceptors in rats. To study these mechanisms, we recorded perfusion pressure and the activities of phrenic and thoracic sympathetic nerves in male juvenile rats using the working heart-brainstem preparation. The time of inspiration significantly increased in SAD rats, and this change was not dependent on the carotid bodies or on the vagal afferents. However, no changes were observed in the perfusion pressure or in the baseline thoracic sympathetic nerves in all phases of the respiratory cycle in SAD rats. Our data show that despite longer inspiratory activity, the baseline sympathetic activity is maintained at a normal level in SAD rats. These findings indicate that the respiratory-sympathetic coupling is normal after SAD and suggest that the respiratory modulation of sympathetic activity is maintained within the normal range after the removal of arterial baroreceptors.

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“…; Souza et al . ). In the present study, the levels of sympathetic outflow during the three respiratory phases of the respiratory cycle were normal in SAD compared with Sham rats.…”

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 98%

Changes in the inspiratory pattern contribute to modulate the sympathetic activity in sino‐aortic denervated rats

Amorim

Bonagamba

Souza

et al. 2017

Experimental Physiology

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“…Chronic intermittent hypoxia (CIH) is an experimental model of repetitive peripheral chemoreceptor activation (Braga, Soriano, & Machado, ; Fletcher, ; Fletcher et al., ; Moraes et al., ; Prabhakar, Peng, Jacono, Kumar, & Dick, ; Zoccal, Bonagamba, Oliveira, Antunes‐Rodrigues, & Machado, , Zoccal, Bonagamba, Paton, & Machado, ). Long‐term exposure to intermittent hypoxia has been shown to lead to sustained hypertension in male and female rats (Fletcher et al., ; Moraes et al., ; Perim, Bonagamba, & Machado, ; Souza, Bonagamba, Amorim, Moraes, & Machado, , ; Souza, Amorim, Moraes, & Machado, ; Zoccal, Bonagamba, Antunes‐Rodrigues, & Machado, , Zoccal et al., 2007b, , ). Several lines of evidence indicate that CIH‐induced hypertension in rats is caused, at least in part, by increased sympathetic outflow, because it can be prevented by 6‐hydroxydopamine‐induced sympathetic denervation, adrenal demedullation and bilateral renal artery denervation (Bao et al., ; Fletcher, Lesske, Oilman, Miller, & Unger, ; Lesske, Fletcher, Bao, & Unger, ).…”

Section: Introductionmentioning

confidence: 99%

Cardiovascular and respiratory profiles during the sleep–wake cycle of rats previously submitted to chronic intermittent hypoxia

Bazilio

Bonagamba

Moraes

et al. 2019

Experimental Physiology

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New Findings What is the central question of this study?Chronic intermittent hypoxia (CIH) causes increased arterial pressure (AP), sympathetic overactivity and changes in expiratory modulation of sympathetic activity. However, changes in the short‐term sleep–wake cycle pattern after CIH and their potential impact on cardiorespiratory parameters have not been reported previously. What is the main finding and its importance?Exposure to CIH for 10 days elevates AP in wakefulness and sleep but does not cause major changes in short‐term sleep–wake cycle pattern. A higher incidence of muscular expiratory activity was observed in rats exposed to CIH only during wakefulness, indicating that active expiration is not required for the increase in AP in rats submitted to CIH. Abstract Chronic intermittent hypoxia (CIH) increases arterial pressure (AP) and changes sympathetic–respiratory coupling. However, the alterations in the sleep–wake cycle after CIH and their potential impact on cardiorespiratory parameters remain unknown. Here, we evaluated whether CIH‐exposed rats present changes in their short‐term sleep–wake cycle pattern and in cardiorespiratory parameters. Male Wistar rats (∼250 g) were divided into CIH and control groups. The CIH rats were exposed to 8 h day−1 of cycles of normoxia (fraction of inspired O2 = 0.208, 5 min) followed by hypoxia (fraction of inspired O2 = 0.06, 30–40 s) for 10 days. One day after CIH, electrocorticographic activity, cervical EMG, AP and heart rate were recorded for 3 h. Plethysmographic recordings were collected for 2 h. A subgroup of control and CIH rats also had the diaphragm and oblique abdominal muscle activities recorded. Chronic intermittent hypoxia did not alter the time for sleep onset, total time awake, durations of rapid eye movement (REM) and non‐REM (NREM) sleep and number of REM episodes in the 3 h recordings. However, a significant increase in the duration of REM episodes was observed. The AP and heart rate were increased in all phases of the cycle in rats exposed to CIH. Respiratory frequency and ventilation were similar between groups in all phases, but tidal volume was increased during NREM and REM sleep in rats exposed to CIH. An increase in the incidence of active expiration during wakefulness was observed in rats exposed to CIH. The data show that CIH‐related hypertension is not caused by changes in the sleep–wake cycle and suggest that active expiration is not required for the increase in AP in freely moving rats exposed to CIH.

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“…Altered cardio-respiratory coupling following exposure to CIH is observed in both sexes, but interestingly the aberrant signature differs between the sexes (Souza et al, 2016). Concerning the issue of sex-related susceptibility to airway collapsibility, CIH-induced pharyngeal dilator muscle weakness was observed in male but not female rats in a model of moderate sleep-disordered breathing (Skelly et al, 2012a).…”

Section: Cih-induced Upper Airway Muscle Dysfunction Is Sex-dependentmentioning

confidence: 97%

Sex, stress and sleep apnoea: Decreased susceptibility to upper airway muscle dysfunction following intermittent hypoxia in females

O’Halloran

Lewis

McDonald

2017

Respiratory Physiology & Neurobiology

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Inspiratory modulation of sympathetic activity is increased in female rats exposed to chronic intermittent hypoxia

Cited by 24 publications

References 42 publications

Changes in the inspiratory pattern contribute to modulate the sympathetic activity in sino‐aortic denervated rats

Changes in the inspiratory pattern contribute to modulate the sympathetic activity in sino‐aortic denervated rats

Cardiovascular and respiratory profiles during the sleep–wake cycle of rats previously submitted to chronic intermittent hypoxia

Sex, stress and sleep apnoea: Decreased susceptibility to upper airway muscle dysfunction following intermittent hypoxia in females

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