This paper reports on the use of arrays of nanoelectrodes to measure activity of the Sympathetic Nervous System. Measurements of the Sympathetic Nervous Activity (SNA) have not been easy; primarily because of poor signal-to-noise ratio (SNR). We report improved SNR of SNA measurements achieved by the use of novel Planar Nanoelectrode Arrays (PNA). Nano scale features on the electrodes provide increased contact area with the host nerve reducing the limiting (Johnson) noise. These electrodes are fabricated using standard CMOS compatible fabrication techniques on a high resistivity silicon substrate and used to measure SNA in test animals. For comparison, traditional wire electrodes were used simultaneously to measure the same signal. The PNAs consistently exhibit significant improvement in the SNR of the measured SNA (35.71 dB vs. 25.08 dB for the wire electrode). Moreover, the PNAs are capable of recording events lost in the noise floor of the wire electrodes.