Bladder and urethral pressures evoked by microstimulation of the sacral spinal cord in cats

Experiments were conducted to measure the bladder and urethral pressures ev oked by intraspinal microstimulation of the sacral segments (S1-S2) in neur ologically intact, chloralose anesthetized adult male cats. The bladder pre ssure was measured with a superpubic catheter and the urethral pressure was measured simultaneously at the level of the urethral sphincter and at the level of the penis using a two-element micromanometer. Intraspinal stimuli (typically 1 s, 20 Hz, 100 mu A, 100 mu s) were applied with activated irid ium microwire electrodes in ipsilateral segments and intersegmental boundar ies with a 250 mu m mediolateral resolution and a 200 mu m dorsoventral res olution. Increases in bladder pressures were generated by microstimulation in the intermediolateral region, in the lateral and ventrolateral ventral h orn, and around the central canal. Simultaneous increases in urethral press ure were evoked by microstimulation in the ventrolateral ventral hem, but n ot at the other locations. Small reductions in urethral pressure (<10 cm H2 O) were evoked at locations in the intermediate laminae and around the cent ral canal. The magnitude of these pressure reductions was weakly dependent on the stimulus parameters. Stimulation around the central canal produced b ladder contractions with either no change or a reduction in urethral pressu re and voiding of small amounts of fluid. These results demonstrate that re gions are present in the spinal intact anesthetized cat where microstimulat ion generates selective contraction of the bladder without increases in ure thral pressure and that regions are present where microstimulation generate s small reductions in urethral pressure. (C) 1999 Elsevier Science B.V. All rights reserved.