Dopamine and FMRFamide act directly on isolated gill muscle fibers in culture.

The peripheral nervous system (PNS) in the gill of Aplysia plays an important role in the mediation of adaptive gill withdrawal reflex (GWR) behaviors. It has proven difficult to determine whether or not neuronally active agents work directly on PNS neurons, the muscle or both. We have now been able to isolate individual gill muscle fibers in culture and thus begin an analysis of how endogenous neurotransmitters and/or neuromodulators act. We report here that both dopamine and FMRF-amide act directly on gill muscle fibers to cause contractions.