Fig. 9.

Specificity of EUS recordings. A: EUS EMG recorded with the implanted electrodes in 9 of the unanesthetized rats used in the present study after receiving midthoracic or lower-thoracic/upper-lumbar spinal cord transections during voiding. Each of these rats had exhibited weak EUS bursting before transection (average % bursting power range: 8.5–10.4%); after transection, they showed strong bursting (% bursting power range: 25–56%; individual values shown adjacent to each trace), strongly suggesting that the electrodes would have been capable of recording bursting had it occurred during pretransection recordings. Calibration: 0.5 s, 30 μV. B: bladder pressure and EUS EMG during cystometry in an acute experiment under ketamine/xylazine anesthesia from an implanted rat after completion of chronic recordings. Although phasic EUS EMG did not usually occur during voiding during chronic recording in this unanesthetized rat, bursting is clearly present in the anesthetized preparation, indicating that the implanted electrodes were properly located for recording from the EUS. A second pair of electrodes, inserted parallel but just lateral to the urethra using a perineal approach, shows similar bursting. The inset shows a magnified view of 2 cycles of bursting recorded from these electrodes. The EMG envelopes of the bursts in the 2 traces are similar although not identical, suggesting that the 2 electrode pairs are recording from different locations within the EUS. C: simultaneous recording of EUS and pubocaudalis muscles in an unanesthetized rat shows little or no correlation in EMG activity between the 2 muscles during voiding. D: compound muscle action potentials (CMAPs) recorded from electrodes chronically implanted adjacent to the EUS (solid line) and in the pubocaudalis muscle on one side (dashed line). Pudendal nerve stimulation elicits a large CMAP from the EUS electrodes, and only a small response from the pubocaudalis electrodes, implying that there is little cross talk between the EUS and pubocaudalis.