Abstract
Recent advances in sensory neuroscience using Drosophila olfaction as a model system have revealed partial map for the representation of the external world within its brain. Currently, three levels of wiring in antenna lobe (AL) are known. Odorants are detected by the olfactory sensory neurons (OSNs), located on the antenna (Ant) and maxillary palp (MP), sending axons via the antennal nerve (AN) and the labial nerve (LN), respectively, to AL (Level 1); where the projection neurons (PNs) receive and calculate the information (Level 2) and then relay to the mushroom body (MB) and the lateral horn (LH) (Level 3). Projection neurons convey the information via three tracks: the inner antenna-cerebrum track (iACT), the medial ACT (mACT), the outer ACT (oACT). In order to investigate the detailed anatomy along these tracks, we generate a transgenic fly, UAS-Photoactivatable GFP (PaGFP), which produces PaGFP under GAL4 control. In this study, the first part is to characterize PaGFP in fly brain, including photoactivation and diffusion. The second part is to demonstrate the anatomical applications of PaGFP, such as revealing single glomerulus or the whole AL, following its activation by a two-photon laser at 820 nm. These results illustrate that circuits tracing is feasible in any region we are interested in Drosophila brains. In this way, we discover some new circuits in addition to the typical three tracts of olfactory circuits and find two regions, medial superior (MS) and ventral lateral (VL), which may also connect with AL. Therefore, PaGFP provides us a novel tool tracing neuronal circuitry and mapping the complete network in Drosophila brains.