Abstract
The effects of chronic kidney disease on baroreflex control of renal sympathetic nerve activity (RSNA) and deficits in afferent and central components of the baroreflex were studied in juvenile and adult male Lewis Polycystic Kidney (LPK) and control Lewis rats under anesthesia (n=35). Blood pressure (BP), heart rate (HR), aortic depressor nerve activity (ADNA), and RSNA were determined after pharmacological manipulation of BP. Responses to ADN stimulation (4.0 V, 2.0 ms, 1-24 Hz) were determined, and the aortic arch was collected for histomorphometry. In juvenile LPK versus age-matched Lewis rats, gain of RSNA (-1.5 +/- 0.2 versus -2.8 +/- 0.2%/mm Hg; P<0.05) and ADNA (2.5 +/- 0.3 versus 5.0 +/- 0.6%/mm Hg; P<0.05), but not HR barocurves, were reduced. BP, HR, and RSNA responses to ADN stimulation were normal or enhanced in juvenile LPK. In adult LPK versus age-matched Lewis, the gain and range of RSNA (gain: -1.2 +/- 0.1 versus -2.2 +/- 0.2%/mm Hg, range: 62 +/- 8 versus 98 +/- 7%) and HR (gain: -0.7 +/- 0.1 versus -3.5 +/- 0.7 bpm/mm Hg, range: 44 +/- 8 versus 111 +/- 19 bpm) barocurves were reduced (P<0.05). The gain and range of the ADNA barocurves were also reduced in adult LPK versus Lewis [1.5 +/- 0.4 versus 5.2 +/- 1.1 (%/mm Hg) and 133 +/- 35 versus 365 +/- 61 (%) P<0.05] and correlated with aortic arch vascular remodeling. BP, HR, and RSNA responses to ADN stimulation were significantly reduced in adult LPK. Our data demonstrate a deficit in the afferent component of the baroreflex that precedes the development of impaired central regulation of RSNA and HR in chronic kidney disease, and that progressive impairment of both components is associated with marked dysfunction of the baroreflex pathway.