Light-gated cation-selective membrane channels are amongst the most popular tools to stimulate neuronal activityin vivo. Here, we used Channelrhodopsin-2 (ChR-2; Nagel et al., 2003) to activate motorneurons of aliveDrosophila melanogasterlarvae by generating action potentials in a well-defined timeframe. While previous work has used light stimulation of motorneurons of fully-grownDrosophilalarvae, these studies focussed on timescales ranging from minutes till just over an hour (Ataman et al., 2008; Pulver et al., 2009). However, it is unknown how neuromuscular synapses react following much longer exposure to light-stimulation.

We evolved an environment to activate the light-gated channels throughout the full larval developmental period. Following such chronic activation of neuromuscular transmission, immunohistochemical tools are used to analyse activity-dependent morphological changes like the area of the NMJ and the number of synapses.

Nagel G, Szellas T, Huhn W, Kateriya S, Adeishvili N, Berthold P, Ollig D, Hegemann P, Bamberg E (2003) Channelrhodopsin-2, a directly light-gated cation-selective membrane channel.PNAS100(24): 13940–5.

Ataman B, Ashley J,Gorczyca M, Ramachandran P, Fouquet W, Sigrist SJ, Budnik V (2008)Rapid Activity-Dependent Modifications in Synaptic Structure and Function Require Bidirectional Wnt Signaling.Neuron57(5): 705–18.

Pulver SR, Pashkovski SL, Hornstein NJ, Garrity PA, Griffith LC (2009)Temporal dynamics of neuronal activation by Channelrhodopsin-2 and TRPA1 determine behavioral output in Drosophila larvae.J Neurophysiol101: 3075–3088.