title: Differential expression of synapsin in visual neurons of the locust Schistocerca gregaria.
abstract: In many taxa, photoreceptors and their second-order neurons operate with graded changes in membrane potential and can release neurotransmitter tonically. A common feature of such neurons in vertebrates is that they have not been found to contain synapsins, a family of proteins that indicate the presence of a reserve pool of synaptic vesicles at synaptic sites. Here, we provide a detailed analysis of synapsin-like immunoreactivity in the compound eye and ocellar photoreceptor cells of the locust Schistocerca gregaria and in some of the second-order neurons. By combining confocal laser scanning microscopy with electron microscopy, we found that photoreceptor cells of both the compound eye and the ocellus lacked synapsin-like immunostaining. In contrast, lamina monopolar cells and large ocellar L interneurons of the lateral ocellus were immunopositive to synapsin. We also identified the output synapses of the photoreceptors and of the L interneurons, and, whereas the photoreceptor synapses lacked immunolabeling, the outputs of the L interneurons were clearly labeled for synapsin. These findings suggest that the photoreceptors and the large second-order neurons of the locust differ in the chemical architecture of their synapses, and we propose that differences in the time course of neurotransmission are the reason for this.
authors.affiliation: Institut für Zellbiologie, Histologie und Embryologie, Medizinische Universität Graz, 8010 Graz, Austria. gerd.leitinger@meduni-graz.at
authors.forename: Gerd
authors.initials: G
authors.lastname: Leitinger
authors.forename: Maria Anna
authors.initials: MA
authors.lastname: Pabst
authors.forename: F Claire
authors.initials: FC
authors.lastname: Rind
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Simmons
mesh_terms: D000818:Animals; D005123:Eye / Q000378:metabolism* / Q000648:ultrastructure; D006110:Grasshoppers / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D007395:Interneurons / Q000378:metabolism / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D009899:Optic Lobe, Nonmammalian / Q000378:metabolism* / Q000648:ultrastructure; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism* / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D016704:Synapsins / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology; D013572:Synaptic Vesicles / Q000378:metabolism / Q000648:ultrastructure; D014795:Visual Pathways / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D016704:Synapsins