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A transfer function method for the continuous assessment of the baroreflex control of renal sympathetic nerve activity in conscious rats
Author(s) -
Kanbar Roy,
Orea Valerie,
Chapuis Bruno,
Barres Christian,
Julien Claude
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.a880-a
In rats, renal sympathetic nerve activity (RSNA) shows a strong rhythmicity at heart rate (HR) frequency which is entirely mediated by the arterial baroreceptor reflex. The present study examined whether the gain of the transfer function relating the cardiac‐related RSNA rhythm to the arterial pressure (AP) pulse might serve as a spontaneous index of sympathetic baroreflex sensitivity (BRS). AP and RSNA were simultaneously recorded in conscious unrestrained rats, either baroreceptor‐intact (control, n = 11) or with partial (aortic) denervation of baroreflex afferents (n = 10). The transfer gain was calculated over 58 adjacent 62‐s periods (segmented each into 10.2‐s periods). Transfer gain was decreased (P = 0.005) in aortic denervated compared with control rats (1.48 ± 0.22 vs. 2.39 ± 0.13 normalized units/mmHg). In the pooled study sample, the mean transfer gain correlated with BRS estimated by the vasoactive drug injection technique (R = 0.75; P < 0.0001) and was inversely related to both time‐ (standard deviation; R = −0.74; P = 0.0001) and frequency‐domain (total spectral power; R = −0.81; P < 0.0001) indices of AP variability. In control rats, the transfer gain exhibited large fluctuations (CV: 34 ± 3 %) that were not consistently related to changes in the mean level of AP, HR or RSNA. In conclusion, the transfer function method provides a continuous index of BRS and reveals that the latter fluctuates widely over time.