Cyclic guanosine monophosphate modulates locomotor acceleration induced by nitric oxide but not serotonin in Clione limacina central pattern generator swim interneurons

Typically, the marine mollusk, Clione limacina, exhibits a slow, hovering locomotor gait to maintain its position in the water column.  However, the animal exhibits behaviorally relevant locomotor swim acceleration during escape response and feeding behavior.  Both nitric oxide and serotonin mediate this behavioral swim acceleration.  In this study, we examine the role that the second messenger, cGMP, plays in mediating nitric oxide and serotonin induced swim acceleration.  We observed that application of an analogue of cGMP or an activator of soluble guanylyl cyclase, increased fictive locomotor speed recorded from Pd-7 interneurons of the animal’s locomotor central pattern generator. Moreover, inhibition of soluble guanylyl cyclase decreased fictive locomotor speed.  These results suggest that basal levels of cGMP are important for slow swimming and that increased production of cGMP mediates swim acceleration in Clione.  Because nitric oxide has its effect through cGMP signaling and b...