Neural and vascular interaction in renin response to graded renal nerve stimulation

The effect of a 1-min period of renal nerve stimulation was studied in alpha-chloralose-anesthetized cats, whose left kidneys were pump perfused. Renal hemodynamics and filtration parameters were unaltered at stimulation frequencies of 2.0 Hz or less; however, renin secretion rates (RSR) increased with frequency reaching 3 times the control level. At higher frequencies renal vasoconstriction occurred and glomerular filtration rate (GFR) fell. RSR was increased but little more than at 2.0 Hz. The RSR response plots were similar to constant-flow and constant-pressure perfused preparations. beta-Adrenergic blockade with propranolol abolished low-frequency responses and resulted in progressive decreases in RSR at higher frequencies. alpha-Adrenergic blockade with phentolamine prevented renal vascular and GFR changes, whereas RSR continually increased up to 12.0 Hz (13.5 times control). Papaverine treatment, to prevent vascular-GFR changes without blocking alpha-receptors, resulted in similar renin responses. The results indicate that the beta-adrenergic receptor mediates increases in RSR in proportion to frequency when vascular-GFR factors are constant. When renal vasoconstriction occurs at high frequencies the beta-receptor mechanism interacts with an inhibiting mechanism indirectly mediated by alpha-adrenergic receptors.