Cardiovascular and autonomic profile of awake mice submitted to sustained hypoxia.

Cardiovascular and autonomic profile of awake mice submitted to sustained hypoxia.

• Autor
• Juliana Reis Souza
• Co-autores
• Mauro de Oliveira , Benedito Honório Machado
• Resumo

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  We documented that mice submitted to short-term sustained hypoxia (SH) presented a significant reduction in baseline heart rate (HR), increased bradycardic response to chemoreflex activation, and increased cervical vagus activity, suggesting an autonomic imbalance in favor of the parasympathetic component. However, whether the observed reduction in baseline HR was due to an increase the parasympathetic tone to the heart was not evaluated.

              The aim of the present study was to evaluate the cardiovascular and autonomic profile of awake mice submitted to SH. For this, C57BL/6 mice under anesthesia had catheters inserted into the femoral artery for recording arterial pressure (MAP) and jugular vein for drug administration. After the surgery, mice were submitted to normoxia or SH protocol (24h, FiO2 0.1). At the end, the cardiovascular responses to sequential autonomic blockade of parasympathetic tone to the heart (methyl-atropine; 1mg/Kg,iv) and sympathetic tone to the heart (propranolol; 3mg/Kg,iv) and arterioles (prazosin; 1mg/Kg,iv) were recorded. Statistical analysis was performed by non-paired Student's t test and non-parametric Mann–Whitney test. All experimental protocols were approved by institutional ethical committee (#140/2019).

              Mice of the SH group (n=8) presented a significant increase in the baseline HR after methyl-atropine (184±84 vs 67±38 bpm, P=0.005) but no major changes in the baseline MAP (-7±8 vs -9±10 mmHg, P=0.7445) when compared to the control (n=7). Mice from control and SH groups presented similar cardiovascular responses to propranolol and prazosin.

              We are showing that SH in mice produces an autonomic imbalance favoring the parasympathetic tone to the heart, which explain the significant reduction in the baseline HR. However, the tachycardic response to the blockade of the parasympathetic tone to the heart produced no changes in baseline MAP, indicating that the lack of hypertension in mice submitted to SH is due mechanisms other than an increased parasympathetic tone to the heart.

   

• Palavras-chave
• Mice C57BL/6, sustained hypoxia, parasympathetic tone, sympathetic tone, cardiovascular system.
• Área Temática
• Vídeo-pôster / Sala 8 -Mod Neural e Hormonal Cardiovascular e Inflamação

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