Meeting Abstract

P2.90  Tuesday, Jan. 5  The Effect of 5-hydroxytryptamine on Each Region of the Alimentary Canal of Lumbricus terrestris NEAL, M.W.*; KRAJNIAK, K.G.; Southern Il. Univ. Edwardsville; Southern Il. Univ. Edwardsville mneal@siue.edu

Previously our lab has shown that neurotransmitters modulate the motility of the isolated crop-gizzard of the earthworm L. terrestris. 5-hydroxytryptamine (5-HT) was found to inhibit spontaneous contractions of the combined crop-gizzard. Since the role of 5-HT in controlling the rest of the digestive tract has yet to be explored, we decided to examine the effects of this neurotransmitter on the isolated pharynx, esophagus, crop, gizzard, and intestine. The organ of choice was removed from the animal and placed in a tissue bath. Contractions were measured with a force transducer, and analyzed with LabScribe. Aliquots of 5-HT, increasing in concentration, were added to the tissue bath, and the resulting changes in contractions were used to create log-dose response curves. We found that 5-HT decreased contraction amplitude and frequency of the pharynx (threshold between 0.1 and 1.0 µM), and crop (threshold between 0.1 and 1.0 µM). The esophagus responded with two phases of inhibition, during the first phase threshold was between 0.1 and 1.0 pM and during the second phase threshold was between 10 and 100 µM. 5-HT increased frequency and decreased amplitude of intestinal contractions (threshold between 0.1 and 1.0 µM). We are currently investigating the effects of 5-HT on the motility of the gizzard.