Sole smooth muscle states determine gliding rate in the freshwater snail Lymnaea stagnalis.
The sole of crawling gastropods is a unique model for studying the function of smooth muscles and ciliated epithelium. The gastropod snail Lymnaea stagnalis glides over the substratum without visible muscular contraction in its sole; consequently, the gliding was thought to be due to sole cilia. However, we have shown that the sole muscles in Lymnaea are phasic smooth muscles. They contribute extensively to gliding rate, which is directly correlated with the sole length (longitudinal sole muscle tonus) that varies widely during gliding. Here, we show that the linear relationship between gliding rate and sole length in Lymnaea may be modified. Serotonin increases gliding rate and has no effect on sole length. Dopamine contracts the sole and, consequently, slows the gliding rate, while ergometrine (a blocker of dopamine receptors) relaxes the sole and increases gliding rate. These influences on locomotion rate and sole length are similar to those obtained earlier for Helix lucorum, in which the substances changed the number and contraction force of muscle cells involved in peristaltic locomotory waves. Taken together, the data obtained here for Lymnaea and earlier for Helix describe the fundamental mechanisms for controlling phasic smooth muscles.
A. N. Belozersky Institute of Physico-Chemical Biology, M. V. Lomonosov Moscow State University, Moscow 119992, Russia.
Galina A
GA
Pavlova
D000818:Animals; D004298:Dopamine / Q000494:pharmacology; D015259:Dopamine Agents / Q000494:pharmacology; D008124:Locomotion / Q000502:physiology*; D008195:Lymnaea / Q000033:anatomy & histology / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
D015259:Dopamine Agents; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D004298:Dopamine