Generation of slow waves in the antral region of guinea-pig stomach - a stochastic process

1. Slow waves were recorded from the circular muscle laver of the antral re gion of guinea-pig stomach. Slow waves were abolished by 2APB, an inhibitor of IP3-induced Ca2+ release. 2. When the rate of generation of slow waves was monitored it was found to vary from cycle to cycle around a mean value. The variation persisted after abolishing neuronal activity xvith tetrodotoxin. 3. When simultaneous recordings were made from interstitial cells in the my enteric region (ICCMY) and smooth muscle cells of the circular layer, varia tions in the rate of generation of slow waves were found to be linked with variations in the rate of generation of driving potentials by ICCMY. 4. A preparation was devised which consisted of the longitudinal muscle lay er and ICCMY. In this preparation ICCMY and smooth muscle cells lying in th e longitudinal muscle laver generated driving potentials and follower poten tials, synchronously. 5. Driving potentials had two components, a rapid primary component that wa s followed by a prolonged plateau component. Caffeine (3 mM) abolished the plateau component; conversely reducing the external concentration of calciu m ions [Ca2+](o) mainly affected the primary component. 6. Analysis of the variations in the rate of generation of driving potentia ls indicated that this arose because both the duration of individual drivin g potentials and the interval between successive driving potentials varied. 7. It is suggested that the initiation or pacemaker activity in a network o f is a stochastic process, with the probability of initiating a driving pot ential slowly increasing, after a delay, from a low to a higher value follo wing the previous driving potential.