Spontaneous slow wave and contractile activity of the guinea pig prostate

Purpose: We characterized the electrical events underlying spontaneous contractions of the stroma of the guinea pig prostate. Materials and Methods: Membrane potential of the stroma was recorded using standard electrophysiological recording techniques. The structure of the prostate was viewed using confocal or electron microscopy. Results: In stromal cells spontaneous depolarizing membrane transients (12 mV. in amplitude) occurred at 5 minutes(-1) and triggered 1 or more spikes. The membrane potential, and frequency and duration of the potential transients were not affected by the calcium channel blocker nifedipine (1 p,M. for greater than 5 minutes), or blockers of neuronal propagation (tetrodotoxin), and the effects of cholinergic (atropine), adrenergic (guanethidine or prazosin) and sensory blockers (capsaicin) of neurotransmission. However, the amplitude of the superimposed spikes was significantly reduced by nifedipine. A network of c-Kit immunoreactive cells was evident in the interstitial layer between the stroma and glandular lined lumen. These prostatic interstitial cells contained many morphological features distinguishing interstitial cells of Cajal, the pacemaker cells of the gastrointestinal tract. Prostatic interstitial cells formed close appositions with each other, with neighboring smooth muscle cells and with varicose axon bundles. Conclusions: Movement of the contents of the peripheral prostatic acini into the minor and major prostatic ducts is likely to occur via spontaneous contractions triggered by myogenic slow wave activity in the stromal wall. By analogy with the intestine and urethra prostatic interstitial cells may well act as the pacemaker for prostatic slow waves as well as form an intercellular communication network interacting with the intrinsic nerves and stromal cells.