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Histamine-immunoreactive local neurons in the antennal lobes of the hymenoptera.

ABSTRACT: Neural networks receive input that is transformed before being sent as output to higher centers of processing. These transformations are often mediated by local interneurons (LNs) that influence output based on activity across the network. In primary olfactory centers, the LNs that mediate these lateral interactions are extremely diverse. For instance, the antennal lobes (ALs) of bumblebees possess both gamma-aminobutyric acid (GABA)- and histamine-immunoreactive (HA-ir) LNs, and both are neurotransmitters associated with fast forms of inhibition. Although the GABAergic network of the AL has been extensively studied, we sought to examine the anatomical features of the HA-ir LNs in relation to the other cellular elements of the bumblebee AL. As a population, HA-ir LNs densely innervate the glomerular core and sparsely arborize in the outer glomerular rind, overlapping with the terminals of olfactory receptor neurons. Individual fills of HA-ir LNs revealed heavy arborization of the outer ring of a single "principal" glomerulus and sparse arborization in the core of other glomeruli. In contrast, projection neurons and GABA-immunoreactive LNs project throughout the glomerular volume. To provide insight into the selective pressures that resulted in the evolution of HA-ir LNs, we determined the phylogenetic distribution of HA-ir LNs in the AL. HA-ir LNs were present in all but the most basal hymenopteran examined, although there were significant morphological differences between major groups within the Hymenoptera. The ALs of other insect taxa examined lacked HA-ir LNs, suggesting that this population of LNs arose within the Hymenoptera and underwent extensive morphological modification.

SUBMITTER: Dacks AM

PROVIDER: S-EPMC2886666 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature

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Histamine-immunoreactive local neurons in the antennal lobes of the hymenoptera.

Dacks Andrew M AM Reisenman Carolina E CE Paulk Angelique C AC Nighorn Alan J AJ

The Journal of comparative neurology 20100801 15

Neural networks receive input that is transformed before being sent as output to higher centers of processing. These transformations are often mediated by local interneurons (LNs) that influence output based on activity across the network. In primary olfactory centers, the LNs that mediate these lateral interactions are extremely diverse. For instance, the antennal lobes (ALs) of bumblebees possess both gamma-aminobutyric acid (GABA)- and histamine-immunoreactive (HA-ir) LNs, and both are neurot ...[more]

PMID: 20533353

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Project description:The paired box gene Pox neuro (Poxn) is expressed in two bilaterally symmetric neuronal clusters of the developing adult Drosophila brain, a protocerebral dorsal cluster (DC) and a deutocerebral ventral cluster (VC). We show that all cells that express Poxn in the developing brain are postmitotic neurons. During embryogenesis, the DC and VC consist of only 20 and 12 neurons that express Poxn, designated embryonic Poxn-neurons. The number of Poxn-neurons increases only during the third larval instar, when the DC and VC increase dramatically to about 242 and 109 Poxn-neurons, respectively, virtually all of which survive to the adult stage, while no new Poxn-neurons are added during metamorphosis. Although the vast majority of Poxn-neurons express Poxn only during third instar, about half of them are born by the end of embryogenesis, as demonstrated by the absence of BrdU incorporation during larval stages. At late third instar, embryonic Poxn-neurons, which begin to express Poxn during embryogenesis, can be easily distinguished from embryonic-born and larval-born Poxn-neurons, which begin to express Poxn only during third instar, (i) by the absence of Pros, (ii) their overt differentiation of axons and neurites, and (iii) the strikingly larger diameter of their cell bodies still apparent in the adult brain. The embryonic Poxn-neurons are primary neurons that lay out the pioneering tracts for the secondary Poxn-neurons, which differentiate projections and axons that follow those of the primary neurons during metamorphosis. The DC and the VC participate only in two neuropils of the adult brain. The DC forms most, if not all, of the neurons that connect the bulb (lateral triangle) with the ellipsoid body, a prominent neuropil of the central complex, while the VC forms most of the ventral projection neurons of the antennal lobe, which connect it ipsilaterally to the lateral horn, bypassing the mushroom bodies. In addition, Poxn-neurons of the VC are ventral local interneurons of the antennal lobe. In the absence of Poxn protein in the developing brain, embryonic Poxn-neurons stall their projections and cannot find their proper target neuropils, the bulb and ellipsoid body in the case of the DC, or the antennal lobe and lateral horn in the case of the VC, whereby the absence of the ellipsoid body neuropil is particularly striking. Poxn is thus crucial for pathfinding both in the DC and VC. Additional implications of our results are discussed.

Project description:BackgroundOdorant-binding proteins (OBPs) are essential in insect's daily behaviors mediated by olfactory perception. Megachile saussurei Radoszkowski (Hymenoptera, Megachilidae) is a principal insect pollinating alfalfa (Medicago sativa) in Northwestern China. The olfactory function have been less conducted, which provides a lot of possibilities for our research.ResultsOur results showed that 20 OBPs were identified in total. Multiple sequence alignment analysis indicated MsauOBPs were highly conserved with a 6-cysteine motif pattern and all belonged to the classic subfamily, coding 113-196 amino acids and sharing 41.32%-99.12% amino acid identity with known OBPs of other bees. Phylogenetic analysis indicated there were certain homologies existed among MsauOBPs and most sequences were clustered with that of Osmia cornuta (Hymenoptera, Megachilidae). Expression analysis showed the identified OBPs were mostly enriched in antennae instead of other four body parts, especially the MsauOBP2, MsauOBP3, MsauOBP4, MsauOBP8, MsauOBP11 and MsauOBP17, in which the MsauOBP2, MsauOBP4 and MsauOBP8 presented obvious tissue-biased expression pattern. Molecular docking results indicated MsauOBP4 might be the most significant protein in recognizing alfalfa flower volatile 3-Octanone, while MsauOBP13 might be the most crucial protein identifying (Z)-3-hexenyl acetate. It was also found the lysine was a momentous hydrophilic amino acid in docking simulations.ConclusionIn this study, we identified and analyzed 20 OBPs of M. saussurei. The certain homology existed among these OBPs, while some degree of divergence could also be noticed, indicating the complex functions that different MsauOBPs performed. Besides, the M. saussurei and Osmia cornuta were very likely to share similar physiological functions as most of their OBPs were clustered together. MsauOBP4 might be the key protein in recognizing 3-Octanone, while MsauOBP13 might be the key protein in binding (Z)-3-hexenyl acetate. These two proteins might contribute to the alfalfa-locating during the pollination process. The relevant results may help determine the highly specific and effective attractants for M. saussurei in alfalfa pollination and reveal the molecular mechanism of odor-evoked pollinating behavior between these two species.

Dataset Information

Histamine-immunoreactive local neurons in the antennal lobes of the hymenoptera.

Publications

Histamine-immunoreactive local neurons in the antennal lobes of the hymenoptera.

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