P3.184 Friday, Jan. 6 Modulation of leech muscle performance by serotonin FEILICH, KL*; GERRY, SP; ELLERBY, DJ; Wellesley College email@example.com
The obliquely striated muscle in the leech body wall has a broad functional repertoire; it provides power for both locomotion and suction feeding. Increased serotonin (5-HT) levels promote these behaviors and also affect muscle mechanical performance. During isometric contractions 5-HT enhances active force production and reduces resting muscle tone. 5-HT may therefore increase net work output during the cyclical contractions associated with locomotion and feeding. Body wall longitudinal strains were measured by sonomicrometry during swimming, crawling and feeding. The resulting strain patterns were applied to longitudinal strips of body wall muscle in vitro using an ergometer and the timing and duration of stimulation selected to maximize net work output. The presence of 5-HT significantly increased net work output during simulated swimming, crawling, and feeding relative to the saline control condition. Without 5-HT the muscle strips could not achieve a net positive work output during simulated swimming. The behavioral and mechanical effects of serotonin are clearly complementary: promoting particular behaviors and enhancing muscle performance during those behaviors.