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Effect of lesions in the nucleus tractus solitarius (NTS) on hypercapnic ventilatory response (HCVR) in awake rats
Author(s) -
Wilkinson Katherine A.,
Fu Zhenxing,
Powell Frank L.
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-d
Subject(s) - saporin , microinjection , chemoreceptor , hypoxic ventilatory response , ventilation (architecture) , substance p , central chemoreceptors , anesthesia , medicine , plethysmograph , endocrinology , chemistry , respiratory system , receptor , neuropeptide , biochemistry , immunotoxin , cytotoxicity , engineering , in vitro , mechanical engineering
To test the physiological significance of CO 2 ‐sensitive neurons identified in the NTS, we measured the HCVR using barometric pressure plethysmography on unrestrained rats breathing 0, 5 and 7% CO 2 in 21% O 2 after bilateral NTS lesions with microinjection (200 nL) of substance P‐saporin conjugates (SP‐SAP, n = 15). For controls we microinjected a conjugate of saporin and an 11 amino acid nonsense peptide (blank, n = 9). Because chronic hypoxia also affects CO 2 ‐sensitivy, we studied rats acclimatized to PI O2 = 70 Torr for 7 days (CH; SP‐SAP n = 10; blank n = 7). ANOVA showed significant effects of SP‐SAP, CH and inspired CO 2 on ventilation, with a significant interaction between SP‐SAP and inspired CO 2 . SP‐SAP decreased the HCVR mainly by an effect on tidal volume, as previously reported for SP‐saporin lesions in the retrotrapezoid nucleus ( J. Physiol. 544:603–616, 2002). Immunohistochemistry for the Neurokinin‐1 receptor is being used to identify the nature and extent of SP‐SAP lesions. Results show a physiological role for chemoreceptors in the NTS but more experiments are necessary to decide if chemoreceptors in the NTS versus other sites play a unique role in ventilatory acclimatization to hypoxia. Supported by NIH HL 17731, 07212, 81823 and UC WMRS.