Assessment of bladder sensation in mice with a novel device

To develop and test the efficacy of an implantable bladder electrode device that can be used with the Neurometer electrodiagnostic stimulator to assess fiber-specific afferent bladder sensation in the mouse.

We constructed a ball-tipped platinum electrode and surgically implanted it into the mouse bladder. The Neurometer was connected to the electrode to apply selective nerve fiber stimuli (250 Hz for Aδ fibers and 5 Hz for C fibers) of increasing intensities to the bladder mucosa in the mouse to determine bladder sensory threshold (BST) values. Using 58 female C57BL/6J mice, we measured the temporal and interobserver consistency of BST measurements, the effects of intravesical administration of lidocaine and resiniferatoxin on the BST, and the effects of our device on voiding behavior and bladder mucosal integrity.

BST values at 250 and 5 Hz did not vary significantly when measured 2, 4, and 6 days after device implantation, or when obtained by 2 blinded independent observers. Intravesical lidocaine yielded a transient increase in BST values at both 250 Hz and 5 Hz, whereas resiniferatoxin yielded a significant increase only at the 5 Hz stimulus frequency after 24 hours. Moderately increased micturition frequency and decreased volume per void were observed 4 and 6 days after device implantation. Histology revealed mild inflammatory changes in the area of the bladder adjacent to the implanted BST device.

Assessment of neuroselective bladder sensation in mice is feasible with our device, which provides reproducible BST values for autonomic bladder afferent nerve fibers.