Meeting Abstract
P1.134 Sunday, Jan. 4 The Cholinergic Receptor Transduction System in the Earthworm Gizzard MEREDITH, AM*; KRAJNIAK, KG; Southern Illinois Univ. Edwardsville ameredi@siue.edu
In the earthworm, Lumbricus terrestris, acetylcholine stimulates the contraction rate of the crop-gizzard and causes a biphasic change in amplitude with an increase at low concentrations and a decrease at high concentrations. Since many cholingeric receptors are linked to the production of second messengers we decided to see if known inhibitors of transduction pathways could alter the mechanical responses of isolated gizzard rings to acetylcholine stimulation. When exposed to the adenylyl cyclase inhibitor, MDL-12,330A, the rate of contraction after an acetylcholine application was markedly decreased. Even after all of the inhibitor was washed away, the subsequent application of acetylcholine did not result in a contraction amplitude as high as the initial 10-6 M application of acetylcholine. These results suggest that a cyclic AMP pathway might be responsible for acetylcholine induced responses. They also suggest that the earthworm gizzard receptor may not be linked to the same second messenger system found in mammals where acetylcholine causes a decrease in the cyclic AMP due to the inhibition of adenylyl cyclase.
