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Inhibitory input from slowly‐adapting lung receptors (SARs) to retrotrapezoid nucleus (RTN) chemoreceptors.
Author(s) -
Takakura Ana Carolina,
Moreira Thiago Santos,
Colombari Eduardo,
Guyenet Patrice G
Publication year - 2007
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.21.6.a917
Subject(s) - muscimol , chemoreceptor , inhibitory postsynaptic potential , agonist , glutamate receptor , neuroscience , neuron , anesthesia , medicine , biology , endocrinology , chemistry , receptor
This study was designed to test whether central chemoreceptors might be inhibited by lung mechanoreceptors. In halothane‐anesthetized artificially ventilated rats (100% O 2 ) with intact vagus nerves, many CO 2 ‐sensitive RTN neurons were markedly inhibited by lung inflation (2–6 cm H 2 O) and those cells were instantly activated by interrupting ventilation. The neurons most sensitive to lung inflation had a marked pump‐related discharge pattern at rest with inhibition during lung inflation. Bilateral injection of the GABA‐A agonist muscimol into the ventrolateral NTS (vlNTS) desynchronized PND from the ventilation cycle and eliminated both the inhibitory effect of lung inflation on RTN neurons and their pump–related pattern. Muscimol injection into vlNTS had little effect on the CO 2 threshold and CO 2 sensitivity of RTN neurons. Bilateral muscimol injection 1.5 mm caudal to RTN (rVRG) eliminated PND but changed neither the pump modulation of RTN neurons nor their inhibition by lung inflation nor their threshold and sensitivity to CO 2 . Glutamate receptor blockade with kynurenate icv (kyn) eliminated PND, RTN neuron pump rate and RTN neuron inhibition by lung inflation but had marginal effects on RTN CO 2 threshold (lowering) and sensitivity to CO 2 (increase). Finally, SAR‐responsive RTN neurons expressed Phox2b. In conclusion, many RTN chemoreceptors receive an inhibitory input from SARs. This input could be disynaptic via vlNTS inhibitory pump cells. Supported by: HL 74011 (PGG); Capes‐BEX 4402/05‐7 (ACT).