Propagation of pacemaker activity in the XXXX antrum.

@entity840 @entity4524 @entity15258 @entity3360 @entity141 @entity20048
Cyclical periods of depolarization (slow waves) underlie peristaltic contractions involved in mixing and emptying of contents in the gastric antrum. Slow waves originate from a myenteric network of interstitial cells of Cajal (ICC-MY). In this study we have visualized the sequence and propagation of @entity141 transients associated with pacemaker potentials in the ICC network and longitudinal (LM) and circular muscle (CM) layers of the isolated @entity840 gastric antrum. Gastric antrum was dissected to reveal the ICC-MY network, loaded with @entity20048 AM and activity was monitored at 37 degrees C. @entity141 waves propagated throughout the ICC-MY network at an average velocity of 3.24 +/- 0.12 mm s(-1) at a frequency of 4.87 +/- 0.16 cycles min(-1) (n= 4). The propagation of the @entity141 wave often appeared 'step-like', with separate regions of the network being activated after variable delays. The direction of propagation was highly variable (Delta angle of propagation 44.3 +/- 10.9 deg per cycle) and was not confined to the axes of the longitudinal or circular muscle. @entity141 waves appeared to spread out radially from the site of initiation. The initiating @entity141 wave in ICC-MY was correlated to secondary @entity141 waves in intramuscular interstitial cells of Cajal, ICC-IM, and smooth muscle cells, and the local distortion (contraction) in a field of view. @entity4524 (1 microm) had little effect on slow wave or pacemaker potential activity, but @entity15258 (50 microm) blocked all @entity141 waves, indicating a pivotal role for intracellular @entity141 stores. @entity3360 (2 microm) eliminated the @entity141 transient generated by smooth muscle, but did not affect the fast upstroke associated with ICC-MY. These results indicate that slow waves follow a sequence of activation, beginning with the ICC-MY and ICC-IM network, followed later by a sustained @entity141 transient in the muscle layers that is responsible for contraction.
