Synaptic Electrophysiology of the Drosophila Neuromuscular Junction

Chemical synaptic transmission is an importa11t means of neuronal communication in the nervous system. On the arrival of an action potential, the nerve terminal experiences an influx of calcium ions, which in turn trigger the exocytosis of synaptic vesicles (SVs) and the release of neurotransmitters into the synaptic cleft. Transmitters elicit synaptic responses in the postsynaptic cell by binding to and activating specific receptors. This is followed by the recycling of SV s at presynaptic terminals. The Drosophila larval neuromuscular junction (NMJ) shares many structural and functional similarities to synapses in other animals, including humans. These include the basic feature of synaptic transmission, as well as the molecular mechanisms regulating the synaptic vesicle cycle. Because of its large size, easy accessibility, and the well-characterized genetics, the fly NMJ remains an excellent model system for dissecting the cellular and molecular mechanisms of synaptic transmission. In this chapter, we describe the theory and practice of electrophysiology as applied to the Drosophila larval Int roduct ion, 172 Box 1. Electrical Terminology, 172 Box 2. Basic Equations and RC Circu its, 173 The Resting Membrane Potential, 175 Synaptic Transmission, 181 Using Drosophila Larval NMj to Study Synaptic Transmission, 183 Protocol 1: Electrophys iological Recording from a "Model" Cell, 188 Protocol 2: Recording from Drosophila Larval Body Wall Muscles: Passive M embrane Properties and Basic Features of Synaptic Transmission, 193 Protocol 3: Voltage-Clamp Analysis of Synaptic Transmission at the Drosophila Larval NMj , 200 Box 3. A Few Words of Caution Concerni ng Voltage-Clamp Experiments, 201 Protocol 4: Focal Recording of Synaptic Currents from Single Boutons at the Larval NMj, 204 Protocol 5: Fabrication of Microelectrodes, Suct ion Electrodes, and Focal Electrodes, 206