Long‐term recording of sympathetic nerve activity using telemetry in conscious rats.

Many studies have implicated sympathetic nerve activity (SNA) as a major factor involved in the regulation of arterial pressure (AP) and the development of hypertension. However, studies have typically been limited by successful recordings in conscious rats for relatively short periods (hours‐days) after instrumentation. Longer recording is required to explain the role of SNA in the development of cardiovascular disease. Our study describes a telemetry system (Telemetry Research Ltd., www.telemetryresearch.com ) that allows long‐term recording of SNA in conscious rats and the complications associated with direct cabling. We instrumented rats with renal SNA electrodes and repeatedly recorded SNA responses to acute cold water stress (1 min. exposure, 1 cm deep), to pharmacological stress with cocaine (5 mg/kg, i.v.), to ganglionic blockade with trimethaphan (10–20 μg/kg, i.v.) to assess background activity in recordings, and to baroreceptor stimuli (phenylephrine at 0.5, 1, 2 μg/kg, iv and nitroprusside at 2, 3, 6 μg/kg, iv). Responses to stressors included reproducible changes in renal SNA corresponding to changes in AP. After two weeks, viable nerve recordings were recorded in most rats studied. This study shows the ability to record renal SNA for at least two weeks in conscious rats. We suggest this technique could provide novel insight into the role of SNS in regulating AP. Supported by USPHS DA13256.