AmOA1 in the Honey Bee Brain Figure 8. Tangential GABAergic neurons in the central complex express the AmOA1 receptor. A: A frontal section of the central complex labeled with anti-octopamine (OA). Octopamine in is present in the ellipsoid body and the fan shaped body. B: Frontal section adjacent to the section shown in A labeled with anti-AmOA1 antibodies. The AmOA1 immunoreactivity is in the tangential fibers that invade the ellipsoid body. Note the fan shaped body is less intensely stained than the ellipsoid body. C: GABA-like immunoreactivity in the tangential neurons innervating the ellipsoid body and fan shaped body. D. Section adjacent to section C double stained with GABA antiserum (D1, green) and anti-AmOA1 antibodies (D2, magenta) revealed that GABAergic processes in the ellipsoid body are co-labeled with AmOA1 receptor (white in merged images) in D3. Scale bar: 25 mm. doi:10.1371/journal.pone.0014536.g008 (Fig. 2). Staining in dendritic and axonal profiles is consistent with expression of the receptor on membranes in those areas. Staining in or close to cell bodies could be due to expression of functional receptors on the cell body membranes, which would be consistent with parasynaptic release of octopamine [70]. It could also be due to trafficking of receptors for transport either to the periphery for insertion into the membrane or from the periphery for degradation. The expression pattern is consistent with results from in situ hybridization [43], which showed the presence of Amoa1 transcripts in the Kenyon cells, cells in the optic lobes and the deutocerebrum with highly variable levels of expression. The widespread expression of the AmOA1 receptor is consistent with a role for this receptor in a number of behaviors modulated by octopamine. AmOA1 in the antennal lobe Behavioral studies demonstrating that RNAi mediated down regulation of AmOA1 expression leads to a reduction in Figure 9. Schematic view of the visual and olfactory pathways in the honey bee mushroom body calyx. The figure was made after [34,54,60–63]. co, collar; br, basal ring; LH, lateral horn, l-ACT, lateral antenna-cerebral tract; m-ACT median antenna-cerebral tract; ASOT, anterior superior optic tract; AN, antennal nerve; CB, central body; M, medial lobe; V, vertical lobe; c, gamma lobe; LIN, local interneurons; VUMmx1, ventral unpaired median neuron in maxillary neuromere; lo-lobula; me-medulla; m, median; l, lateral; r-rostral; c-caudal. Scale bar: 250 mm. doi:10.1371/journal.pone.0014536.g009 PLoS ONE | www.plosone.org 12 January 2011 | Volume 6 | Issue 1 | e14536