Continuous long‐term recording of renal (RSNA) and lumber (LSNA) sympathetic nerve activity and arterial pressure (AP) in conscious rats: Responses to chronic angiotensin II (AngII) administration

We measured long‐term RSNA, LSNA and AP responses to either AngII (150 ng/kg/min, s.c.) or vehicle (VEH) in rats consuming a high salt diet (2.0% NaCl). Rats were instrumented with an electrode on the renal or lumbar nerve and a telemetry transmitter for measurement of SNA and AP respectively. Beginning 7 days later, RSNA, LSNA and AP were measured continuously for 4 days before and 11 days during AngII or VEH. RSNA results: Control AP (mmHg) was similar in VEH (103 ± 2; N= 5) and AngII (105 ± 3; N=6) rats. On Day 1 of AngII, AP was increased (122 ± 6) whereas RSNA was decreased 26 % from control levels. AP and RSNA did not change in VEH rats on Day 1. On Day 10 of AngII, AP remained elevated (127 ± 9) and RSNA was reduced 30% from control. By day 10 of vehicle, AP was 103 ± 3 and RSNA was 121% of control levels. LSNA results: Baseline AP was similar in VEH (108 ± 3; N=3) and AngII (107 ± 4; N=4) rats. On Day 1 of AngII, AP increased (128 ± 6) and LSNA remained unchanged (94 ± 6% of control). By day 10 of AngII, AP remained elevated (151 ± 7) but LSNA was not different than control (91 ± 9 %). AP and LSNA did not change in VEH rats over the entire protocol. We conclude that AngII‐salt hypertension is associated with long‐term differential responses of renal and lumbar SNA.