Distribution of neuropeptides in the primary olfactory center of the heliothine moth Heliothis virescens

Abstract

Neuropeptides are a diverse widespread class of signaling substances in the nervous system. As a basis for the analysis of peptidergic neurotransmission in the insect olfactory system, we have studied the distribution of neuropeptides in the antennal lobe of the moth Heliothis virescens. Immunocytochemical experiments with antisera recognizing A-type allatostatins (AST-As), Manduca sexta allatotropin (Mas-AT), FMRFamide-related peptides (FaRPs), and tachykinin-related peptides (TKRPs) have shown that members of all four peptide families are present in local interneurons of the antennal lobe. Whereas antisera against AST-As, Mas-AT, and FaRPs give similar staining patterns characterized by dense meshworks of processes confined to the core of all antennal-lobe glomeruli, TKRPs are present only in neurons with blebby processes distributed throughout each glomerulus. In addition to local neurons, a pair of centrifugal neurons with cell bodies in the lateral subesophageal ganglion, arborizations in the antennal lobe, and projections in the inner antenno-cerebral tracts exhibits tachykinin immunostaining. Double-label immunofluorescence has detected the co-localization of AST-As, Mas-AT, and FaRPs in certain local interneurons, whereas TKRPs occurs in a distinct population. MALDI-TOF mass spectrometry has revealed nearly 50 mass peaks in the antennal lobe. Seven of these masses (four AST-As, two N-terminally extended FLRFamides, and Mas-AT) match known moth neuropeptides. The data thus show that local interneurons of the moth antennal lobe are highly differentiated with respect to their neuropeptide content. The antennal lobe therefore represents an ideal preparation for the future analysis of peptide signaling in insect brain.

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

“…A recent study on the distribution of various neuropeptides in the adult AL of the noctuid moth Heliothis virescens revealed about the same numbers of neuropeptide immunoreactive neurons in the lateral cell group for the same three antisera used in the various M. sexta studies (Mas-AT: *87; AST-A: *47; RFamide: *64; Berg et al, 2007). Double immunostainings with antisera against Mas-AT and AST-A or RFamide antisera using the same method as in the current study, revealed a similar number of neurons which colocalize Mas-AT and AST-A (*32) but only about half of the number which colocalize Mas-AT and RFamide (*15) immunoreactivity.…”

“…Direct profiling of ALs of several insects including M. sexta, Heliothis virescens, Apis mellifera, and the beetle Tribolium castaneum by MALDI-TOF mass spectrometry suggests about 40-50 different neuropeptides in the ALs of each of these species (Berg et al, 2007;Utz et al, 2007;and unpublished). Neuropeptides have often been considered as cotransmitters that are released in concert with a principal transmitter (Vilim et al, 2000;Nässel, 2002).…”

“…Mass spectrometric analysis of neuropeptides in the ALs of M. sexta, Heliothis virescens, the honeybee, and Tribolium castaneum even suggest about 40-50 different neuropeptides in the ALs of each of these species (Berg et al, 2007;Utz et al, 2007;and unpublished). Neuropeptides might operate as cotransmitters of GABA (c-aminobutyric acid), the principle transmitter of local AL interneurons .…”

“…For triple-labeling, the anti-Mas-AT, anti-GABA, and antisynapsin antibodies were applied simultaneously and, likewise, the corresponding secondary antisera. Double labeling with anti-Mas-AT and anti-Dip-AST7 or anti RFamide antisera was performed according to a method modified from Negoescu et al (1994), for double immunolabeling with primary antisera from the same species as recently described in Berg et al (2007).…”

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

“…Bicker, 1999;Homberg, 2002;Schachtner et al, 2005;Berg et al, 2009;Fusca et al, 2015). 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.…”