title: Serotonergic neurons in the nucleus raphe obscurus contribute to interaction between central and peripheral ventilatory responses to hypercapnia.
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.
authors: Department of Physiology, University of São Paulo(USP/FMRP), Ribeirão Preto, SP, Brazil. glauber@rfi.fmrp.usp.br
authors: Glauber S F
authors: GS
authors: da Silva
authors: Humberto
authors: H
authors: Giusti
authors: Maurício
authors: M
authors: Benedetti
authors: Mirela B
authors: MB
authors: Dias
authors: Luciane H
authors: LH
authors: Gargaglioni
authors: Luiz Guilherme S
authors: LG
authors: Branco
authors: Mogens L
authors: ML
authors: Glass
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002344:Carotid Body / Q000166:cytology / Q000502:physiology; D002628:Chemoreceptor Cells / Q000502:physiology; D006935:Hypercapnia / Q000378:metabolism*; D008297:Male; D010100:Oxygen / Q000097:blood; D012123:Pulmonary Ventilation / Q000502:physiology*; D011903:Raphe Nuclei / Q000166:cytology* / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration; D059326:Serotonergic Neurons / Q000166:cytology / Q000378:metabolism* / Q000473:pathology
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen