Role of glutamatergic neurons and interneurons of the lateral parafacial region of mice in the control of expiratory and inspiratory activities, and pulmonary ventilation.

Abstract

Under resting conditions and from the point of view of thorax and abdomen motor activity, expiration is a passive process that becomes active in situations of high ventilatory demand, such as during hypercapnia/acidosis. In these conditions, phasic motor activity of muscles in the abdominal region is observed, promoting an increase in tidal volume and pulmonary ventilation, favoring the air outflow from the lungs. Studies have shown that the lateral parafacial region (pFL) is crucial to generate the expiratory motor activity induced by hypercapnia/acidosis. The pFL region contains heterogeneous populations of glutamatergic, GABAergic, and glycinergic neurons and interneurons (with local projections). Some evidence points to a subpopulation of glutamatergic neurons that are silent under resting conditions due to postsynaptic inhibition. However, these neurons become active at the end of expiration, simultaneously with active expiration, in response to hypercapnia/acidosis. Such evidence indicates the presence of a complex local network involved in the generation and modulation of active expiration by the pFL region. However, the functional contribution to the generation of active expiration of the pFL glutamatergic neurons and interneurons, as well as their electrophysiological properties and connectivity, have not yet been fully clarified. In this context, our hypotheses are that: i) the activation of glutamatergic neurons in the pFL region evokes active expiration and increases pulmonary ventilation under resting conditions, and; ii) inhibition of glutamatergic neurons in the pFL region eliminates active expiration and reduces pulmonary ventilation under conditions of hypercapnia/acidosis. Therefore, we will evaluate the contribution of pFL glutamatergic neurons and interneurons to the generation of inspiratory and expiratory motor activities and the control of pulmonary ventilation, both at rest and during hypercapnia/acidosis. We will also evaluate its projections, electrophysiological properties, and sensitivity to CO2/H+. For this, we will use the site-specific genetically modified mice, which express the cre-recombinase enzyme in glutamatergic neurons, associated with microinjections of adeno-associated viruses for the expression of Design Receptors Exclusively Activated by Designer Drugs, which will allow the activation or inhibition of glutamatergic neurons and interneurons in the pFL region. Inspiratory and expiratory motor activities and pulmonary ventilation will be evaluated in non-anesthetized mice. The electrical properties of glutamatergic interneurons in the pFL region will be evaluated using the whole cell patch clamp technique. The results obtained with this Project will be crucial for a better understanding of the cellular mechanisms by which the glutamatergic neurons of the pFL region contribute to the generation of active expiration and, consequently, to its impact on pulmonary ventilation.