Mas‐allatotropin in the developing antennal lobe of the sphinx moth Manduca sexta: Distribution, time course, developmental regulation, and colocalization with other neuropeptides

Abstract

ABSTRACT:The paired antennal lobes (ALs) of the sphinx moth Manduca sexta serve as a well-established model for studying development of the primary integration centers for odor information in the brain. To further reveal the role of neuropeptides during AL development, we have analyzed cellular distribution, developmental time course, and regulation of the neuropeptide M. sexta allatotropin (Mas-AT). On the basis of morphology and appearance during AL formation, seven major types of Mas-AT-immunoreactive (ir) cells could be distinguished. Mas-AT-ir cells are identified as local, projection, and centrifugal neurons, which are either persisting larval or newly added adult-specific neurons. Complementary immunostaining with antisera against two other neuropeptide families (A-type allatostatins, RFamides) revealed colocalization within three of the Mas-AT-ir cell types. On the basis of this neurochemistry, the most prominent type of Mas-AT-ir neurons, the local AT neurons (LATn), could be divided in three subpopulations. The appearance of the Mas-AT-ir cell types occurring during metamorphosis parallels the rising titer of the developmental hormone 20-hydroxyecdysone (20E). Artificially shifting the 20E titer to an earlier developmental time point resulted in the precocious occurrence of Mas-AT immunostaining. This result supports the hypothesis that the pupal rise of 20E is causative for Mas-AT expression during AL development. Comparing localization and developmental time course of Mas-AT and other neuropeptides with the time course of AL formation suggests various functions for these neuropeptides during development, including an involvement in the formation of the olfactory glomeruli. '

γ-Aminobutyric acid immunostaining in the antennal lobe of the moth Heliothis virescens and its colocalization with neuropeptides

“…The colocalization of these peptides and GABA in a large number of cell bodies in the lateral cell cluster therefore indicates that many GABA-immunoreactive neurons are local neurons. This is in full agreement with previous reports in the sphinx moth M. sexta and several other insect species (Hoskins et al 1986;Homberg et al 1989; for reviews, see Homberg and Müller 1999;Utz et al 2008). The inhibitory effect of GABA was demonstrated for the moth antennal lobe more than 20 years ago (Waldrop et al 1987).…”

“…In M. sexta, two large somata with positions similar to those in H. virescens have been labeled with antisera against Mas-AT and FMRFamide but are devoid of GABA immunoreactivity. They have been assigned as somata of projection neurons sending their axons to the tritocerebrum and probably the subesophageal ganglion (Schachtner et al 2004;Utz et al 2008). …”

Novel antennal lobe substructures revealed in the small hive beetle Aethina tumida

“…The synapsin antibody was kindly provided by Dr. Erich Buchner (University of Würzburg, Germany), was first described by Klagges et al (1996), and used in many insect studies to label neuropilar F o r P e e r R e v i e w 5 areas (e.g. Utz et al, 2008;Heuer et al, 2012;Binzer et al, 2014). The antibody was used at a dilution of 1:100.…”

“…In addition AL neurons contain neuromediators like biogenic amines, gaseous signaling molecules like NO and a large variety of neuropeptides suggesting important involvement for proper olfactory behavior (e.g. Schachtner et al, 2005;Berg et al, 2007;Utz et al, 2008;Carlsson et al, 2010;Binzer et al, 2014;Siju et al, 2014;Fusca et al, 2015). For example, in moths and flies serotonin (5HT) is able to modulate the sensitivity of odors and sex pheromones (Linn and Roelofs, 1986;Gatellier et al, 2004;Hill et al, 2003;Kloppenburg andHildebrand, 1995, Dacks et al, 2009).…”

Conservation of the function counts: homologous neurons express sequence‐related neuropeptides that originate from different genes

“…As primary antibodies, we used a polyclonal anti-Pea-periviscerokinin-2 (PVK-2) serum raised in rabbit at a concentration of 1 : 4000 (kindly provided by Dr M. Eckert, Jena) (Predel et al 1998). To selectively label neuropil structures, we applied a monoclonal anti-synapsin I antibody (SYNORF1; 1 : 100; kindly provided by Dr E. Buchner, Würz-burg); its specificity in M. sexta was demonstrated recently (Utz et al 2008). Antisera were diluted in PBST containing 1% NGS and 0.02% sodium azide and applied together for 8.5 days at 4°C.…”