Meeting Abstract

P3.77  Saturday, Jan. 5  Modulation of swimming in Clione limacina by nitric oxide involves spike narrowing in central pattern generator interneurons WALTON, D.B.*; WILLINGHAM, K.A.; PIRTLE, T.J.; Abilene Christian University; Abilene Christian University; Abilene Christian University Thomas.Pirtle@acu.edu

Modulation of a central pattern generator�s activity produces changes in its output such as varying frequency. Two neuromodulatory transmitters, serotonin and nitric oxide, function in the pteropod mollusk, Clione limacina, to produce acceleration in swimming. Both serotonin and nitric oxide modify the activity of the swim interneurons comprising Clione�s swim central pattern generator. Serotonin was previously shown to cause a decrease in the spike duration of swim interneurons (spike narrowing). By applying the nitric oxide donor, DEA/NO (10 micromolar), we have shown that nitric oxide induced acceleration is accompanied with spike narrowing. Application of the cyclic GMP analog, 8-bromo-cyclic GMP (1 millimolar), also results in acceleration and spike narrowing. To test the hypothesis that nitric oxide works through cyclic GMP we administered the inhibitor of nitric oxide sensitive guanylyl cyclase, ODQ (20 micromolar), prior to adding DEA/NO. DEA/NO application following ODQ did not decrease spike duration, but had the unexpected effect of increasing spike duration. These experiments demonstrate that serotonin and nitric oxide function in a similar way to affect swim acceleration in Clione and suggest that these two signaling pathways may converge to activate guanylyl cyclase. This possibility is currently being investigated.