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Phox2b‐expressing neurons of the retrotrapezoid nucleus regulate post‐inspiration in conscious mice
Author(s) -
Flor Karine,
Oliveira Luiz,
Takakura Ana,
Moreira Thiago
Publication year - 2021
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2021.35.s1.02803
Subject(s) - tidal volume , ventilation (architecture) , glutamatergic , respiratory rate , stimulation , receptor , breathing , respiratory system , pulmonary stretch receptors , anesthesia , neuroscience , pharmacology , chemistry , medicine , biology , glutamate receptor , blood pressure , heart rate , physics , thermodynamics
The retrotrapezoid nucleus (RTN) contains Phox2b‐expressing glutamatergic neurons that regulate all aspects of breathing in a CO 2 ‐depende manner. In the present study, we hypothesized that neurons in this nucleus would also be involved in the post‐inspiratory phase of the respiratory cycle. Here we use a combination of phamacogenetic and genetic modification mice (Phox2b‐cre +/‐ ) to explore how these neurons control breathing in conscious and anesthetized adult mice. Phox2b‐expressing neurons in the RTN region were targeted with a adeno associate vector to induce the expression of an artificial G(q) protein‐coupled receptor termed designer receptors exclusively activated by designer drugs (DREADD‐Gq). The transduced neurons were activated by systemic administration of otherwise inert ligand clozapine‐n‐oxide (CNO). Breathing measurements were recorded in conscious freely moving mce before and after RTN stimulation. Under baseline conditions, administration of CNO (90 µg/mL ‐ 0.1 mL/animal) increased the respiratory rate (f R : 207.7 ± 25.3 vs. vehicle: 152.3 ± 5.8 bpm), tidal volume (V T : 5.0 ± 0.64, vs. vehicle: 4.1 ± 1.5 mL/kg) and ventilation (V E : 1103.0 ± 234 vs. vehicle: 613.6 ± 40.2 mL/min/kg). The CNO injection was also able to elicit an increase in the post‐inspiratory phase (0.1077 ± 0.023, vs. vehicle: 0.076 ± 0.008) and in the total expiratory phase (0.0992 ± 0.037, vs vehicle: 0.0476 ± 0.018) in Phox2b‐Cre +/‐ mice. In urethane‐anesthetized mice, CNO injection was also able to elicit an increase in intercostal muscle activity (Int EMG : 61 ± 1.3, vs. vehicle: 8 ± 1.4 mV) and an increase in the post‐inspiratory of vagal activity (cVN: 62 ± 1.8, vs. vehicle: 29 ± 1.5 mV) and post‐inspiratory peak of the vagus nerve (cVN peak: 142 ± 4.2, vs. vehicle: 64 ± 1.4 V). Importantly, pharmacogenetic stimulation of the RTN‐Phox2b neurons and a saturating CO₂ concentration produced similar effects on breathing. Therefore, consistent with their anatomical projections, RTN‐Phox2b neurons regulate lung ventilation by controlling all aspects of breathing, i.e breathing frequency, inspiration, post‐inspiration and active expiration.