Intracellular recordings of respiratory and pre‐sympathetic neurons in the ventrolateral medulla of rats submitted to chronic intermittent hypoxia

Sympathetic activity is increased during late‐expiratory (late‐E) phase in CIH rats. Electrophysiological properties of medullary respiratory and pre‐sympathetic neurons were evaluated in CIH rats. At 11 th day, using working heart brainstem preparation, we recorded respiratory and sympathetic nerves simultaneously with intracellular recordings of medullary respiratory and pre‐sympathetic neurons. In CIH rats the decrease in the frequency discharge of Bötzinger post‐inspiratory [post‐I, (n=28)] neurons reduced the post‐I activity of central vagus nerve (n=10). The overactivities of augmenting expiratory [aug‐E, (n=55)] and pre‐Bötzinger pre‐inspiratory [pre‐I, (n=30)] neurons increased the late‐E abdominal (n=28) and pre‐I hypoglossal (n=20) nerves activities. Due to these changes, the frequency discharge of pre‐sympathetic neurons (n=27) and thoracic sympathetic activity (n=30) were enhanced time‐locked with late‐E. However, CIH produced changes in the input resistance and excitability, independent of synaptic transmission only in the pre‐I (p<0.05; n=15) and post‐I (p<0.05; n=17) neurons. These data support the concept that CIH leads to changes in the intrinsic properties of pre‐I and post‐I respiratory neurons, which may contribute to the observed increase in the sympathetic activity in this experimental model. Supported by FAPESP and CNPQ.