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Locus coeruleus participates in amphibian central chemoreception
Author(s) -
Gargaglioni Luciane H.,
NoronhadeSouza Carolina R.,
Bicego Kenia C,
Branco Luiz G. S.
Publication year - 2006
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.20.4.a786-a
Subject(s) - locus coeruleus , hypercarbia , central chemoreceptors , peripheral chemoreceptors , chemoreceptor , hyperventilation , chemistry , endocrinology , amphibian , medicine , ventilation (architecture) , central nervous system , anesthesia , biology , receptor , ecology , hypoxemia , mechanical engineering , engineering
The locus coeruleus (LC) is a mesencephalic structure of the amphibian brain that has been considered to be homologous to the LC of mammals. However, there is no data about the role of LC in the central chemoreception in amphibians as it is in mammals. The present study was designed to investigate whether LC of toads ( Bufo paracnemis ) is activated by hypercarbia (5% CO 2 in air) by using Fos immunoreactivity. Additionally, we investigated the role of noradrenergic LC neurons on cardio‐respiratory responses to hypercarbia. To kill the noradrenergic neurons we administered 6‐OHDA into the LC (n=8). Control animals had acid ascorbic acid (vehicle) injected into the LC (n=6) or had no surgery (n=7). A marked increase in c‐Fos positive cells in the LC was observed after 3 h of breathing a hypercarbic gas mixture. Tyrosine hydroxylase immunoreactive noradrenergic neurons were reduced in the LC after 6‐OHDA treatment. LC lesion did not affect room air ventilation and cardiovascular control. Hypercarbia caused hyperventilation in all 3 groups. However, chemical lesions in the LC attenuated the increase in the ventilatory response to hypercarbia (VE: control: 354.5 ± 69.9; vehicle: 358.2 ± 124.9 and 6‐OHDA: 126.3 ± 26.8 mL BTPS kg −1 min −1 ; One‐way ANOVA), due to a lower tidal volume. We conclude that LC is activated by hypercarbia and that LC noradrenergic neurons of toads participate in the central chemoreception as in mammals. Financial support: FAPESP, CNPq.