Abstract
Serotonergic (5-HT) neurons in the nucleus raphe obscurus (ROb) are involved in the respiratory control network. However, it is not known whether ROb 5-HT neurons play a role in the functional interdependence between central and peripheral chemoreceptors. Therefore, we investigated the role of ROb 5-HT neurons in the ventilatory responses to CO2 and their putative involvement in the central–peripheral CO2 chemoreceptor interaction in unanaesthetised rats. We used a chemical lesion specific for 5-HT neurons (anti-SERT-SAP) of the ROb in animals with the carotid body (CB) intact or removed (CBR). Pulmonary ventilation (V E), body temperature and the arterial blood gases were measured before, during and after a hypercapnic challenge (7% CO2). The lesion of ROb 5-HT neurons alone (CB intact) or the lesion of 5-HT neurons of ROb+CBR did not affect baseline V E during normocapnic condition. Killing ROb 5-HT neurons (CB intact) significantly decreased the ventilatory response to hypercapnia (p < 0.05). The reduction in CO2 sensitivity was approximately 15%. When ROb 5-HT neurons lesion was combined with CBR (anti-SERT-SAP+CBR), the V E response to hypercapnia was further decreased (−31.2%) compared to the control group. The attenuation of CO2 sensitivity was approximately 30%, and it was more pronounced than the sum of the individual effects of central (ROb lesion; −12.3%) or peripheral (CBR; −5.5%) treatments. Our data indicate that ROb 5-HT neurons play an important role in the CO2 drive to breathing and may act as an important element in the central–peripheral chemoreception interaction to CO2 responsiveness.
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Acknowledgements
This research was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) no. 07/51581-2. Glauber S.F. da Silva was supported by FAPESP no. 06/60696-5.
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da Silva, G.S.F., Giusti, H., Benedetti, M. et al. Serotonergic neurons in the nucleus raphe obscurus contribute to interaction between central and peripheral ventilatory responses to hypercapnia. Pflugers Arch - Eur J Physiol 462, 407–418 (2011). https://doi.org/10.1007/s00424-011-0990-x
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DOI: https://doi.org/10.1007/s00424-011-0990-x