Of mice and men - sympathetic recordings in awake and behaving mice

Hamza S., Hall J., (2012). Direct recording of renal sympathetic nerve activity in unrestrained, conscious mice. Hypertension, 60:856-864 Details

Customer study highlights

The kidneys are the conductors of the orchestra when it comes to hypertension. To gain potential therapeutic insight into hypertension and thousands of other diseases that afflict humankind, animal models of human disease are frequently used. Due to the vast number of transgenic mouse models available, the most pervasive animal model used is the mouse.

Mouse models pose particular challenges due to their small size. Previously, recording renal sympathetic nerve activity (RSNA) has required anaesthesia. However anaesthetics can have complex, biphasic effects on autonomic nervous system function, necessitating the use of indirect measures such as HRV instead.

To address this, researchers at the Universities of Alberta and Mississippi have developed a technique to directly measure activity in sympathetic nerves supplying the kidneys in freely-moving mice. These nerve bundles are very small and embedded in the walls of the renal arteries on both sides. Interestingly, in humans with intractable hypertension, sympathectomy of the renal supply can substantially lower blood pressure.

Mice were instrumented with an indwelling catheter containing a custom-made bipolar electrode, which was connected to the left renal nerve bundle. The electrode leads exited through the skin on the left flank, which served as a tether point for RSNA recordings. Blood pressure (BP) was also measured using telemetry from a catheter inserted in the carotid artery.

RSNA signals were amplified x10,000 using a Dagan differential amplifier and sampled along with BP signals using a PowerLab and analyzed in LabChart 7. Successful recordings of RSNA signals were made in ten out of twelve mice. 48 hours post-implantation, RSNA signals had typical burst-firing patterns and remained stable for up to 3-5 days.

Considering the plethora of transgenic mouse models available and the absence of wireless SNA solutions for mice, this exciting technique permits measurement of autonomic activity in awake and freely-moving mice.

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