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GABA immunoreactivity in the antennocerebral tracts of the moth brain. a Horizontal section showing lack of immunostaining in the inner antennocerebral tract. Only two stained axons (arrows) can be seen as they pass the central body (CB). Note part of the middle antennocerebral tract (double arrow). b Fibers in the middle antennocerebral tract (arrows), which projects directly from the antennal lobe (AL) to the lateral protocerebrum (LPC), show prominent GABA immunostaining (Ca calyces of the mushroom
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The antennal lobe is the primary processing center for olfactory information in insects. To understand further the neural circuitry of this brain area, we have investigated the distribution of gamma-aminobutyric acid (GABA) and its colocalization with neuropeptides in the antennal lobe of the noctuid moth Heliothis virescens. Immunocytochemical exp...
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... inner antennocerebral tract projecting from the anten- nal lobe to the calyces of the mushroom body appeared as a thick bundle of unstained axons, except for two immuno- reactive fibers (Fig. 2a). Their target projections in the protocerebrum could not be traced. In contrast to the immunonegative inner antennocerebral tract, the middle . The large cumulus is more sparsely invaded by immunoreactive fibers than the ordinary glomeruli. Bars 50 μm antennocerebral tract (MACT) projecting to the lateral protocerebrum contained a ...
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... in the protocerebrum could not be traced. In contrast to the immunonegative inner antennocerebral tract, the middle . The large cumulus is more sparsely invaded by immunoreactive fibers than the ordinary glomeruli. Bars 50 μm antennocerebral tract (MACT) projecting to the lateral protocerebrum contained a considerable number of labeled axons (Fig. 2b). In the protocerebrum, the stained fiber bundle divided and targeted two different areas (Figs. 2b, 3a). The outer antennocerebral tract targeting the lateral protocerebrum via a more ventrally located pathway (Fig. 3c) also included some GABA-immunolabeled neu- rons, visible as they left the antennal lobe (Fig. 2c). In addition to the ...
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... tract, the middle . The large cumulus is more sparsely invaded by immunoreactive fibers than the ordinary glomeruli. Bars 50 μm antennocerebral tract (MACT) projecting to the lateral protocerebrum contained a considerable number of labeled axons (Fig. 2b). In the protocerebrum, the stained fiber bundle divided and targeted two different areas (Figs. 2b, 3a). The outer antennocerebral tract targeting the lateral protocerebrum via a more ventrally located pathway (Fig. 3c) also included some GABA-immunolabeled neu- rons, visible as they left the antennal lobe (Fig. 2c). In addition to the three main antennocerebral pathways, the dorsal antennocerebral tract running more dorsally appeared as ...
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... number of labeled axons (Fig. 2b). In the protocerebrum, the stained fiber bundle divided and targeted two different areas (Figs. 2b, 3a). The outer antennocerebral tract targeting the lateral protocerebrum via a more ventrally located pathway (Fig. 3c) also included some GABA-immunolabeled neu- rons, visible as they left the antennal lobe (Fig. 2c). In addition to the three main antennocerebral pathways, the dorsal antennocerebral tract running more dorsally appeared as a tight bundle of strongly labeled axons (Figs. 2d-f, 3b). In addition to the protocerebral pathways, a few stained fibers connected the antennal lobe with the antennal mechanosensory and motor center and/or the ...
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... targeting the lateral protocerebrum via a more ventrally located pathway (Fig. 3c) also included some GABA-immunolabeled neu- rons, visible as they left the antennal lobe (Fig. 2c). In addition to the three main antennocerebral pathways, the dorsal antennocerebral tract running more dorsally appeared as a tight bundle of strongly labeled axons (Figs. 2d-f, 3b). In addition to the protocerebral pathways, a few stained fibers connected the antennal lobe with the antennal mechanosensory and motor center and/or the subesophageal ganglion (Fig. ...
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... to the three main antennocerebral pathways, the dorsal antennocerebral tract running more dorsally appeared as a tight bundle of strongly labeled axons (Figs. 2d-f, 3b). In addition to the protocerebral pathways, a few stained fibers connected the antennal lobe with the antennal mechanosensory and motor center and/or the subesophageal ganglion (Fig. ...
Citations
... Since this tract innervates the LH heavily, like the medial-tract PNs, it seems to be closely linked with the most prominent tract. About half of the mlALT PNs utilizes the inhibitory transmitter GABA (Berg et al. 2009;Hoskins et al. 1986), indicating that third-order olfactory neurons in the LH receive convergent excitatory and inhibitory inputs from the medial and mediolateral tracts, respectively-as shown in D. melanogaster (Wang et al. 2014). ...
... Rather, it seems that the dALT in heliothine moths connects only with ordinary glomeruli (unpublished data). Generally, the dALT PNs are reported to be GABAergic (Berg et al. 2009;Hoskins et al. 1986) and they should thereby offer inhibitory signals to several protocerebral neuropils. Thus far, there are only two examples of individually labeled PNs confined to the dALT (Kanzaki et al. 1989;Kymre et al. 2021a). ...
The olfactory pathways of the insect brain have been studied comprehensively for more than 40 years, yet the last decade has included a particularly large accumulation of new information relating to this system’s structure. In moths, sharp intracellular recording and staining has been used to elucidate the anatomy and physiology of output neurons from the primary olfactory center, the antennal lobe. This review concentrates on the connection patterns characterizing these projection neurons, which follow six separate antennal-lobe tracts. In addition to highlighting the connections between functionally distinct glomerular clusters and higher-order olfactory neuropils, we discuss how parallel tracts in the male convey distinct features of the social signals released by conspecific and heterospecific females. Finally, we consider the current state of knowledge regarding olfactory processing in the moth’s protocerebrum and make suggestions as to how the information concerning antennal-lobe output may be used to design future studies.
... This was, perhaps, most clearly demonstrated by the broad response profiles of the mediolateral-tract PNs with evenly distributed dendrites across the MGC ( Figure 5 and Figure 5figure supplement 7). These PNs responded to all female-produced components, but with distinct temporal patterns (Figure 7), and may provide excitatory or inhibitory output since about half of the axons forming this tract are GABAergic (Berg et al., 2009). Furthermore, we demonstrated that these mlALT PNs had overlapping terminals with the medial-tract MGC-PNs in this neuropil ( Figure 4A), indicating the possibility of axo-axonic interaction. ...
The pheromone system of heliothine moths is an optimal model for studying principles underlying higher-order olfactory processing. In Helicoverpa armigera, three male-specific glomeruli receive input about three female-produced signals, the primary pheromone component, serving as an attractant, and two minor constituents, serving a dual function, i.e. attraction versus inhibition of attraction. From the antennal-lobe glomeruli, the information is conveyed to higher olfactory centers, including the lateral protocerebrum, via three main paths – of which the medial tract is the most prominent. In this study, we traced physiologically identified medial-tract projection neurons from each of the three male‑specific glomeruli with the aim of mapping their terminal branches in the lateral protocerebrum. Our data suggest that the neurons’ wide-spread projections are organized according to behavioral significance, including a spatial separation of signals representing attraction versus inhibition – however, with a unique capacity of switching behavioral consequence based on the amount of the minor components.
... The LNs, whose synaptic input and output regions are restricted to the AL, constitute a heterogeneous population of neurons with distinct physiological, morphological, and biochemical properties (Seki and Kanzaki 2008;Chou et al. 2010;Seki et al. 2010;Tabuchi et al. 2015). Typically, they contain a classical transmitter like GABA or ACh and one or more potential co-transmitters like peptides or biogenic amines (Berg et al. 2007(Berg et al. , 2009Shang et al. 2007;Seki and Kanzaki 2008;Ignell et al. 2009;Kreissl et al. 2010;Chou et al. 2010). In P. americana, two main LN types with very different physiological properties can be differentiated (Fig. 4): (1) spiking type I LNs that generated Na + -driven action potentials upon odor stimulation and exhibited GABA-lir and (2) nonspiking type II LNs, in which odor stimulation evoked depolarizations, but no Na + -driven action potentials (Husch et al. 2009a). ...
Highly interconnected neural networks perform olfactory signal processing in the central nervous system. In insects, the first synaptic processing of the olfactory input from the antennae occurs in the antennal lobe, the functional equivalent of the olfactory bulb in vertebrates. Key components of the olfactory network in the antennal lobe are two main types of neurons: the local interneurons and the projection (output) neurons. Both neuron types have different physiological tasks during olfactory processing, which accordingly require specialized functional phenotypes. This review gives an overview of important cell type-specific functional properties of the different types of projection neurons and local interneurons in the antennal lobe of the cockroach Periplaneta americana , which is an experimental system that has elucidated many important biophysical and cellular bases of intrinsic physiological properties of these neurons.
... It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in The copyright holder for this this version posted December 11, 2020. ; https://doi.org/10.1101/2020.12.11.421289 doi: bioRxiv preprint 21 excitatory or inhibitory input to the medial-tract PNs in the VLP since about half of the axons 461 forming this tract is GABAergic (Berg et al., 2009). Furthermore, we demonstrated that these 462 mlALT PNs had overlapping terminals with the medial-tract MGC PNs in this neuropil (Fig. 463 3A). ...
The pheromone system of heliothine moths is an optimal model for studying principles underlying higher-order olfactory processing. In Helicoverpa armigera, three male-specific glomeruli receive input about three female-produced signals, the primary pheromone component, serving as an attractant, and two minor constituents, serving a dual function, i.e. attraction versus inhibition of attraction. From the antennal-lobe glomeruli, the information is conveyed to higher olfactory centers, including the lateral protocerebrum, via three main paths - of which the medial tract is the most prominent. In this study, we traced physiologically identified medial-tract projection neurons from each of the three male specific glomeruli with the aim of mapping their terminal branches in the lateral protocerebrum. Our data suggest that the neurons' wide-spread projections are organized according to behavioral significance, including a spatial separation of signals representing attraction versus inhibition - however, with a unique capacity of switching behavioral consequence based on the amount of the minor components.
... The LNs are axon-less, spatially confined neurons having both input and output synapses in the AL (Christensen, Waldrop, Harrow, & Hildebrand, 1993;Tabuchi et al., 2015). Most LNs are GABAergic (Berg, Schachtner, & Homberg, 2009;Seki & Kanzaki, 2008), providing inhibition to the AL network. Many LNs innervate most of the glomeruli, and were termed MGC-AllGs LNs by Seki and Kanzaki (2008). ...
... The labeled dALT PN had widespread axon terminals and connected to large parts of the AL (Figure 6b). As many dALT and mlALT PNs are GABAergic (Berg et al., 2009), they can provide inhibitory input to many protocerebral regions. Finally, the dmALT PNs resemble the mALT PNs in many ways, including innervation of the calyces and LH (Ian, Zhao, et al., 2016;Kanzaki et al., 1989;Rø et al., 2007). ...
... The fact that 30% of these LNs had substantially sparser innervations in the MGC than in the OGs, is in accordance with findings from M. sexta and B. mori (Matsumoto & Hildebrand, 1981;Seki & Kanzaki, 2008). This indicates a reduced role for LN-mediation in the MGC, yet MGC-PN activity is clearly mediated by GABA (Christensen, Waldrop, & Hildebrand, 1998;Lei, Christensen, & Hildebrand, 2002), which corresponds with the large proportion of GABAergic LNs found across moth species (Berg et al., 2009;Seki & Kanzaki, 2008). The MGC-AllGs LNs further included 26%, 20%, and 14% with sparse or no innervations in the LPOG, PCx, and VPGs, respectively. ...
The relatively large primary olfactory centre of the insect brain, the antennal lobe (AL), contains several heterogeneous neuronal types. These include projection neurons (PNs), providing olfactory information to higher-order neuropils via parallel pathways, and local interneurons (LNs), which provide lateral processing within the AL. In addition, various types of centrifugal neurons (CNs) offer top-down modulation onto the other AL neurons. By performing iontophoretic intracellular staining, we collected a large number of AL neurons in the moth, Helicoverpa armigera, to examine the distinct morphological features of PNs, LNs, and CNs. We characterize 190 AL neurons. These were allocated to 25 distinct neuronal types or sub-types, which were reconstructed and placed into a reference brain. In addition to six PN types comprising 15 sub-types, three LN and seven CN types were identified. High-resolution confocal images allowed us to analyse AL innervations of the various reported neurons, which demonstrated that all PNs innervating ventroposterior glomeruli contact a protocerebral neuropil that is rarely targeted by other PNs, i.e. the posteriorlateral protocerebrum. We also discuss the functional roles of the distinct CNs, which included several previously uncharacterized types, likely involved in computations spanning from multisensory processing to olfactory feedback signalization into the AL.
... the neurotransmitter used by most Pns is understood to be acetylcholine (hoskins et al. 1986;homberg et al. 1988Seki and Kanzaki 2008;Seki et al. 2005;reisenman et al. 2011); acetylcholine will transmit excitatory inputs to the MBcs as well as to the ilPt. two immunocytochemical studies from Manduca sexta and Heliothis virescens, however, have indicated that many, and possibly most, of the Pns traveling over the ml-aPt to the ilPt exhibit GaBa-like immunoreactivity (Glir) (hoskins et al. 1986;Berg et al. 2009). these Pns terminate in the ilPt without continuing on to the MBcs. ...
... In M. sexta and H. virescens, the mlALT is composed of only mPNs, while the lALT and mALT have both u-and mPNs (Homberg et al. 1988;Helge et al. 2007;Ian et al. 2016). Many PNs of the mlALT in both M. sexta and H. virescens have also been shown to be GABAergic (Hoskins et al. 1986;Berg et al. 2009). Similar is the case in Hymenoptera (bees and ants), where uPNs project through lALT and mALT to higher olfactory centers, while mPNs comprise the three mlALTs (Kirschner et al. 2006;Zube et al. 2008;Rössler and Zube 2011). ...
Olfactory systems of different species show variations in structure and physiology despite some conserved features. We characterized the olfactory circuit of the grasshopper Hieroglyphus banian of family Acrididae (subfamily: Hemiacridinae) and compared it to a well-studied species of locust, Schistocerca americana (subfamily: Cyrtacanthacridinae), also belonging to family Acrididae. We used in vivo electrophysiological, immunohistochemical, and anatomical (bulk tract tracing) methods to elucidate the olfactory pathway from the second-order neurons in antennal lobe to the fourth-order neurons in β-lobe of H. banian. We observe conserved anatomical and physiological characteristics through the fourth-order neurons in the olfactory circuit of H. banian and S. americana, though they are evolutionarily divergent (~ 57 million years ago). However, we found one major difference between the two species—there are four antennal lobe tracts in H. banian, while only one is reported in S. americana. Besides, we have discovered a new class of bilateral neurons which respond weakly to olfactory stimuli, even though they innervate densely downstream of Kenyon cells.
... LNs in moths are mainly GABA-ergic and mediate inter-glomerular inhibition and dis-inhibition. Additionally, in H. virescens a small population of non-GABAergic LNs containing the neuropeptide tachykinin has been reported (Berg et al. 2009). Inhibitory LNs is assumed to sharpen odorant representation of PNs by reducing weak afferent input and concurrently allowing responses of glomeruli receiving the strongest input. ...
... Generally, uPNs in moths are mainly excitatory (cholinergic) whereas mPNs are mainly inhibitory (GABAergic) (reviewed by Riffell and Hildebrand 2016). Approximately half of the mlALT PNs in heliothine moths are GABAergic, suggesting that these neurons may inhibit downstream LP neurons (Berg et al. 2009). Therefore, LP receives a combination of feed-forward excitation and inhibition. ...
Herbivorous moth species are important models in studies of olfaction, starting with the pioneering work on the silk moth. Their survival directly depends on innate and learned olfactory cues, both insect produced pheromones and plant odors, for feeding and reproduction (mating and oviposition). Therefore, gaining knowledge about the crucial olfactory system in moth, also contribute to strategies in species-specific pest management. Extensive studies over the last decades have given good insight into the pheromone system. The plant odor sensory system, however, have been challenged by defining the biologically relevant odorants, which is an essential knowledge when aiming to understand complex olfactory coding mechanisms. Many studies have revealed selective plant odor sensory neurons in both female and male moth. The most convincing results demonstrating highly sensitive and narrowly tuned neurons, come from linking chemical analyses to electrophysiological recordings of single units, which has allowed classification of neurons into functional types according to the molecular receptive range, appearing with one primary odorant and a few other structurally similar and less potent secondary odorants. In heliothine moth, the different neuron types barely overlap in their receptive range, though some variation is seen in species of other genera. A comparative study among heliothine species has demonstrated the presence of neuron types with identical specificity, indicating an evolutionary conservation of receptor proteins. Conservation of co-located neuron types in particular sensilla, within and across species, implies the sensillum as a functional unit. According to “the molecular logic of the sense of smell”, it is hypothesized that each of the approximately 70 glomeruli in the moth antennal lobe devoted to plant odor information receive projections from olfactory sensory neurons of the same functional type. It is hypothesized that the response profiles of antennal lobe projection neurons (uni- or multi-glomerular), reflect the molecular receptive ranges of the sensory neurons innervating the particular glomeruli, i.e. responding specifically to the primary odorant of these neurons. Furthermore, the antennal lobe network with local interneurons (predominantly inhibitory) and modulatory centrifugal neurons enhance complexity and flexibility of odor processing. Projection neurons convey antennal lobe output to higher olfactory areas in the protocerebrum mainly via three tracts terminating in the calyces of the mushroom bodies, the lateral horn and two less pronounced areas in the superior protocerebrum and around the peduncle. Plant odorant and pheromone information conveyed in parallel pathways into the antennal lobe, are kept separated in the calyces of the mushroom bodies (involved in learning), and the lateral protocerebrum (an integration area) indicating a functional organization according to behavioral relevance. Neuronal plasticity makes moths able to adjust behavior and adapt to a shifting environment. Altogether, the olfactory sensory system provides the moth with the ability to recognize a variety of plant odorants with high precision. However, the neuronal mechanism explaining how odorants finally generate/release the innate and learned behaviors of attraction, repellency, feeding and oviposition has yet to be resolved.
... These reports concurred that dendritic staining in the MGC was sparser compared to ordinary glomeruli and considerable GABA axonal staining was only visible in mlALT. In M. sexta and H. virescens GABA staining was noted in some lALT axons and only about two fibers in mALT (Berg et al., 2009;Hoskins et al., 1986). Similarly, most fly iPNs exit the AL via the mlALT (iPNs) and project to the LH and VLPN (Tanaka et al., 2012). ...
Olfactory projection neurons convey information from the insect antennal lobe (AL) to higher brain centers. Previous reports have demonstrated that pheromone‐responsive projection neurons with cell bodies in the moth medial cell cluster (mcPNs) predominantly have dendritic arborizations in the sexually dimorphic macroglomerular complex (MGC) and send an axon from the AL to the calyces of the mushroom body (CA) as well as the lateral horn (LH) of the protocerebrum via the medial AL tract. These neurons typically exhibit a narrow odor tuning range related to the restriction of their dendritic arbors within a single glomerulus (uniglomerular). In this study, we report on the diverse physiological and morphological properties of a group of pheromone‐responsive olfactory projection neurons with cell bodies in the AL lateral cell cluster (MGC lcPNs) of two closely related moth species. All pheromone‐responsive lcPNs appeared to exhibit “basket‐like” dendritic arborizations in two MGC compartments and made connections with various protocerebral targets including ventrolateral and superior neuropils via projections primarily through the lateral AL tract and to a lesser extent the mediolateral antennal lobe tract. Physiological characterization of MGC lcPNs also revealed a diversity of response profiles including those either enhanced by or reliant upon presentation of a pheromone blend. These responses manifested themselves as higher maximum firing rates and/or improved temporal resolution of pulsatile stimuli. MGC lcPNs therefore participate in conveying diverse olfactory information relating to qualitative and temporal facets of the pheromone stimulus to a more expansive number of protocerebral targets than their mcPN counterparts.
... Both drugs act as positive allosteric regulators of several ligand-gated channels, including γ-aminobutyric acid (GABA)-gated chloride channels and glutamate-gated chloride channels (GluCl). GABA-gated chloride ion channels are present in neurons and abundant in local interneurons and antennal lobes 1 Scientific REPORTS | (2018) 8:14885 | DOI: 10.1038/s41598-018-33241-0 of insects [5][6][7][8] and are essential for olfactory processing. Furthermore, GABA B receptors have been observed in olfactory sensory neurons in the male antenna of Heliothis virescens (F., 1777), initiating a GABA-mediated gain control mechanism that could play a pivotal role in processing pheromone signals 9 . ...
Abstract Among macrocyclic lactones (ML), ivermectin (IVM) and moxidectin (MOX) potentially affect all Ecdysozoan species, with dung beetles being particularly sensitive. The comparative effects of IVM and MOX on adult dung beetles were assessed for the first time to determine both the physiological sub-lethal symptoms and pre-lethal consequences. Inhibition of antennal response and ataxia were tested as two intuitive and ecologically relevant parameters by obtaining the lowest observed effect concentration (LOEC) values and interpolating other relevant toxicity thresholds derived from concentration-response curves (IC50, as the concentration of each ML where the antennal response is inhibited by half; and pLC50, as the quantity of ingested ML where partial paralysis was observed by half of treated individuals) from concentration-response curves. Both sub-lethal and pre-lethal symptoms obtained in this study coincided in that IVM was six times more toxic than MOX for adult dung beetles. Values of LOEC, IC50 and pLC50 obtained for IVM and MOX evaluated in an environmental context indicate that MOX, despite needing more time for tis elimination in the faeces, would be twice as harmful to dung beetles as IVM. This approach will be valuable to clarify the real impact of MLs on dung beetle health and to avoid the subsequent environmental consequences.
