After recovery, this rabies virus was amplified as efficiently as the SADΔG-GFP rabies virus (10.2

kb genome). While in our hands neither the transgene expressed nor the size of the viral genome prevented production of high-titer ΔG rabies viruses, it is likely that the utility of these viruses will depend on the skill and care taken by those who grow them as well as careful adherence to the established selleckchem protocols we have developed. One of the main goals of systems neuroscience is to understand the architecture and function of neural circuits. Understanding how neural circuits function will require resolving the connectivity of the components; correlating the function of components with their connectivity; manipulating the activity of selected components and monitoring the activity of other components within the networks; and finally, assessing

the behavioral outcome. Techniques for achieving these goals, however, are limited. The rabies tools we have described here provide many new opportunities to allow the combination of rabies-virus-based circuit tracing with functional studies. For example, expression of the calcium sensor GCaMP3 in neurons that have been infected as a result of their connectivity with specific cell types or a single neuron Selleckchem HSP inhibitor could allow observations of direct correlations between connectivity and function in a single living preparation. Here we have explicitly demonstrated this type of approach

by combining retrograde infection with GCaMP3-expressing ΔG rabies virus with in vivo two-photon imaging of visual responses. This allowed measurements of the visual receptive fields of a specific subset of mouse V1 neurons selected on the basis of their connectivity to area AL. Similarly, expression of ChR2 and AlstR should allow control of neural activities in vitro and in vivo and facilitate tests of the causal relationships between connectivity and function within defined neural circuits. It should also be possible to test possible else postsynaptic targets of connectionally-targeted rabies-virus-infected neurons for functional connectivity with potential postsynaptic neurons through intracellular recording combined with photoactivation of axons from neurons expressing ChR2 from the rabies genome (Petreanu et al., 2007). Targeting infection and transsynaptic labeling with GCaMP3-ΔG, ChR2-ΔG, and AlstR-ΔG rabies in defined cell types or single cells with retrograde infection (Stepien et al., 2010, Wickersham et al., 2007a, Wickersham et al., 2007b and Yonehara et al., 2011), Cre-dependent TVA transduction (Haubensak et al., 2010 and Wall et al., 2010), bridge proteins with TVB (Choi et al., 2010), or single cell electroporation of TVA (Marshel et al., 2010 and Rancz et al., 2011) will be extremely useful for functional studies of identified neural circuits.