Neuroscience Letters, 113 (1990) 345-348 345 Elsevier Scientific Publishers Ireland Ltd. NSL 06906 Dopamine and FMRFamide act directly on isolated gill muscle fibers in culture David Cawthorpe and Ken Lukowiak Neuroseience Research Group, Faculty of Medicine, University of Calgary, Calgary, Alta (Canada) (Received 21 December 1989; Revised version received 6 February 1990; Accepted 6 February 1990) Key words." Aplysia; Isolated gill muscle-fiber; Neuropeptide 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 neurotrans- mitters and/or neuromodulators act. We report here that both dopamine and FMRF-amide act directly on gill muscle fibers to cause contractions. Adaptive gill withdrawal reflex (GWR) behaviors in Aplysia are mediated by the integrated activity of the central (CNS) and peripheral (PNS) nervous system [7]. Pri- marily because of the inaccessibility of the PNS in the gill, most of the research dir- ected towards gaining an understanding of the neuronal basis of adaptive GWR be- haviors has focused on the CNS [6]. Although the PNS can be experimentally mani- pulated to effect GWR behaviors by the perfusion of endogenous neurally active agents such as dopamine or FMRFamide through the gill [3, 5, 8] little is known with regard to either the site or mechanism of action of these agonists [9, 10]. As a first step in overcoming these difficulties we have developed a primary culture of disso- ciated gill muscle fibers so that we can test whether these neurally active agents act directly on the gill muscle or indirectly through PNS neurons. Gills were isolated from the animal as previously described [2]. The efferent vein and pieces of the pinnule were then cut away and washed in isotonic antibiotic L-15 medium (Sigma). Under sterile conditions, these tissue samples were washed several times and were finally placed in centrifuge tubes containing L-15 to which 8 mg/ml collagenase (Worthington) had been added. They were then incubated (room temp. or 37°C) until the tissue was observed to disintegrate. The samples were then centri- Correspondence: K. Lukowiak, Neuroscience Research Group, Faculty of Medicine. University of Calg- ary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4NI, Canada. 0304-3940/90/$ 03.50 (~') 1990 Elsevier Scientific Publishers Ireland Ltd.