Aminergical regulation of pheromone sensillae in the cockroach Periplaneta americana

Vast adaptability of insects is provided substantially by fast tining of physiological functioning of an organism to conform to the permanently changing environmental conditions. One of the mechanisms of plasticity in insects is modulation of performance of their sense organs by neurohormones. Activity of at least three out of four receptor cells located in cockroach pheromonesensitive sensilla is under influence of octopamine. Increase in firing rate of pheromone receptor cells and decrease in electroantennogram amplitude is accompanied by enhanced behavioural responses of male cockroaches to sex pheromone. The effect of octopamine on reception of a repellent (1,8-cineole) by an insect is reported for the first time. Simultaneous modulation of responses of receptor cells located in sex specific sensilla to semantically different odorants implies their cooperation in formation of insect's behaviour.     

Activity modulation in cockroach sensillum: the role of octopamine

The plasticity of sensory perception is provided partially by modulation of receptor cells. The electrical activity of American cockroach chemoreceptor cells in response to sex pheromone was measured under the influence of octopamine treatment and tracheal anoxia. Both experimental procedures caused decreased electroantennograms but affected spike activity differently: octopamine treatment increased firing rate, whereas anoxia decreased it. Spike frequency under octopamine treatment was elevated in response to pheromone stimulation and at background activity. Experiments with perfusion of isolated antennae showed a direct effect of octopamine on spike activity of pheromone sensilla, and excluded the possibility of indirect effects via octopamine-dependent release of other biologically active substances. The suggested mechanism of octopamine action is receptor cell membrane depolarization.     

Biogenic amines modulate olfactory receptor neurons firing activity in Mamestra brassicae

The modulatory effects of the biogenic amines octopamine and serotonin on pheromonal receptor neurons of Mamestra brassicae were investigated. The responses to sex pheromone components of two cells types (A and B) in single male long sensilla trichodea were monitored. Cell types A and B do not respond to the same compound. The response of type A to a pulse of the major sex pheromone component increased 5 min after octopamine injection. Responses of type B to other odorants increased after 30 min. In the absence of any pheromone stimulation the background firing activity of type A increased following octopamine injection. This background activity was used to evaluate the kinetics of octopamine and other biogenic amine effects on olfactory receptor neurons. Octopamine increased this background activity in a concentration- and time-dependent manner. Clonidine, an octopamine agonist, was shown to be more powerful in increasing the background activity of olfactory receptor neurons. The effects of octopamine and clonidine were hypothesized to arise from specific receptor activation as chlorpromazine (an octopamine antagonist) was shown to block the effect of octopamine. Serotonin, a known neuromodulator in most animal species, induced a reversible inhibition of spike firing. Altogether, these results indicate that biogenic amines can modulate the sensitivity of olfactory receptor neurons of moths either directly or by an action on adaptation.     

植物源挥发物对昆虫信息素的增效作用及其增效机制

植物源挥发物和昆虫信息素是昆虫的重要信息物质,二者协同作用以调节昆虫的行为.通过增加触角电位、信息素接收神经元动作电位和脉冲频率,特异性植物源挥发物能显著增强昆虫性信息素和聚集信息素的引诱力.这种对昆虫信息素的增效作用受昆虫体内的章鱼胺及其受体介导.特异性植物源挥发物和章鱼胺受体结合,降低性信息素接收神经元对性信息素的反应阈值,增强性信息素接收神经元敏感性.这可能是植物源挥发物对昆虫信息素具有增效作用的主要机制.     

Octopamine and tyramine modulate pheromone-sensitive olfactory sensilla of the hawkmoth <Emphasis Type="Italic">Manduca sexta</Emphasis> in a time-dependent manner

In moths octopamine improved pheromone-dependent mate search time dependently. In the nocturnal hawkmoth Manduca sexta long-term tip recordings of trichoid sensilla were performed to investigate whether biogenic amines modulate pheromone transduction time dependently. At three Zeitgebertimes octopamine, tyramine and the octopamine antagonist epinastine were applied during non-adapting pheromone-stimulation. At ZT 8-11, during the photophase, when sensilla were adapted, octopamine and to a lesser extent tyramine increased the bombykal-dependent sensillar potential amplitude and initial action potential (AP) frequency. In addition, during the photophase, when sensilla are less able to resolve pheromone pulses, octopamine rendered pheromone responses more phasic and sensitive, and raised the spontaneous AP frequency. During the late scotophase, at ZT 22-1, when the antenna appeared maximally sensitized for pheromone pulse detection and endogenous octopamine levels are high, exogenously applied octopamine was ineffective. Epinastine blocked the pheromone-dependent AP response at ZT 8-11 and slightly affected it at ZT 22-1, while it had no effect on the sensillar potential amplitude. Epinastine decreased the spontaneous AP activity during photophase and scotophase and rendered pheromone responses more tonic in the scotophase. We hypothesize that the presence of octopamine in the antenna is obligatory for the detection of intermittent pheromone pulses at all Zeitgebertimes.     

Modulation by octopamine of olfactory responses to nonpheromone odorants in the cockroach, Periplaneta americana L

Olfactory receptor cells in insects are modulated by neurohormones. Recordings from cockroach olfactory sensilla showed that a subset of sensory neurons increase their responses to selected nonpheromone odorants after octopamine application. With octopamine application, recordings demonstrated increased firing rates by the short but not the long alcohol-sensitive sensilla to the nonpheromone volatile, hexan-1-ol. Within the same sensillum, individual receptor cells are shown to be modulated independently from each other, indicating that the octopamine receptors reside in the receptor not in the accessory cells. A uniform decrease in the amplitude of electroantennogram, which is odorant independent, is suggested to reflect the rise in octopamine concentration in the antennal hemolymph. Perception of general odorants measured as behavioral responses changed qualitatively under octopamine treatment: namely, repulsive hexan-1-ol became neutral, whereas neutral eucalyptol became attractive. Octopamine induced a change in male behavioral responses to general odors that were essentially the same as in the state of sexual arousal. Our findings suggest that sensitivity to odors having different biological significances is modulated selectively at the peripheral as well as other levels of olfactory processing.     

Octopamine enhances moth olfactory responses to pheromones, but not those to general odorants

Effects of octopamine on responses of olfactory receptor neurons of Bombyx mori males and females, specialized to the reception of pheromone components and general odorants, respectively, were compared. Injections of octopamine had no effect on the transepithelial potential of antennal sensilla trichodea in both sexes. In males, octopamine increased significantly the amplitude of receptor potentials and nerve impulse responses elicited by the pheromone components bombykol and bombykal. However, the responses of homologous female general odorant-sensitive neurons to linalool and benzoic acid were not affected. In control experiments, injection of physiological saline did not increase the responses in any neuron type.     

Olfactory receptor neurons detecting plant odours and male volatiles in Anomala cuprea beetles (Coleoptera: Scarabaeidae)

We have identified several types of olfactory receptor neurons in male and female Anomala cuprea beetles. The receptor neurons were sensitive to female sex pheromone components, flower volatiles, green leaf volatiles and unknown volatiles from males. Olfactory sensilla were located on three lamellae forming the antennal club. There was a clear spatial separation between some types of sensilla on each lamella. Receptor neurons for the two sex pheromone components were situated in sensilla placodea covering a specific area on each lamella in both males and females. All sex pheromone receptor neurons were found in these sensilla. Most other receptor neurons were located in a longitudinal, heterogeneous streak formed by various types of sensilla. Receptor neurons for plant-derived compounds appeared to be specialists with a high sensitivity to their respective key compound. The most remarkable among these are the green leaf volatile-specific receptor neurons, which were both sensitive and selective, with the key compound being at least 1000 times as effective as any other compound. These green leaf volatile detectors are apparently homologous to detectors recently found in the scarab Phyllopertha diversa. Our results emphasize the role of single-sensillum recordings as a tool in the identification of biologically active odours.     

Mixture interactions in moth olfactory physiology: examining the effects of odorant mixture, concentration, distal stimulation, and antennal nerve transection on sensillar responses

The insect olfactory system is challenged to decipher valid signals from among an assortment of chemical cues present in the airborne environment. In the moth, Heliothis virescens, males rely upon detection and discrimination of a unique blend of components in the female sex pheromone to locate mates. The effect of variable odor mixtures was used to examine physiological responses from neurons within sensilla on the moth antenna sensitive to female sex pheromone components. Increasing concentrations of heliothine sex pheromone components applied in concert with the cognate stimulus for each neuronal type resulted in mixture suppression of activity, except for one odorant combination where mixture enhancement was apparent. Olfactory receptor neuron (ORN) responses were compared between moths with intact and transected antennal nerves to determine whether specific instances of suppression might be influenced by central mechanisms. Type A sensilla showed little variation in response between transected and intact preparations; however, recordings from type B sensilla with transected antennal nerves exhibited reduced mixture suppression. Testing by parallel stimulation of distal antennal segments while recording and stimulating proximal segments dismissed the possibility of interneuronal or ephaptic effects upon sensillar responses. The results indicate that increasing concentrations of "noncognate" odorants in an odor mixture or antennal nerve transection can produce variation in the intensity and temporal dynamics of physiological recordings from H. virescens ORNs.     

Plant-odour-specific receptor neurones on the antennae of female and male Spodoptera littoralis

Abstract. Receptor neurones with high selectivity and sensitivity to plant odours were found within short sensilla trichodea on the antenna of both female and male Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) by using single-sensillum recording techniques. In 112 sensilla from females and forty-one from males, twenty-four different receptor neurone types were characterized according to their specificity. Altogether, twenty-six plant and three sex pheromone compounds were tested. Receptor neurones responding with high specificity to flower odours, green leaf volatiles, oviposition deterrents and other general host plant odours were identified. In twenty-one receptor neurone types, responses were elicited by one or several plant compounds, and in three types responses were elicited by sex pheromone compounds. The majority of the receptor neurones responded to only one or two of the tested compounds. In general, only one of the two receptor neurones in a sensillum responded to any of the compounds tested. An exception was a receptor neurone responding to plant odours (green leaf volatiles) and another receptor neurone responding to a sex pheromone compound ([Z]-7-dodecenyl (acetate), which occurred in the same sensillum. The majority of the receptor neurones displayed a high sensitivity to plant odours. No morphological difference was identified the different sensillum types.     

Perception of potential sex pheromones and host-associated volatiles in the cotton plant bug,Adelphocoris fasciaticollis (Hemiptera: Miridae): morphology and electrophysiology

Highly developed chemoreception allows insects to detect foods, find mates, and escape natural enemies. We described the structures and distributions of antennal chemosensilla in Adelphocoris fasciaticollis Reuter by scanning electron microscopy and transmission electron microscopy. Seven major types of antennal sensilla were identified in adults of both sexes. Types 1 and 2 are sensilla chaetica and have thick cuticular walls with conspicuous grooves at their surfaces. Types 3 and 4 are multiporous sensilla trichodea with 1–3 dendrites located at the sensillum lymph, indicating a putative olfactory function. Types 5 and 6 are typical sensilla basiconica but share different characteristics in both external morphology and internal ultrastructure, and may be involved in the perception of host-associated odorants. The last sensilla were Böhm bristles. In addition to the morphological characterization, electrophysiological responses of antennal chemosensilla to 51 semiochemicals were investigated based on electroantennogram (EAG) recordings. Results revealed that different chemical stimuli elicited significantly different dose-dependent EAG responses, in which potential sex pheromone components and green leaf volatiles showed relatively higher EAG responses, but neither monoterpenes nor sesquiterpenes can elicit favorable EAG values. The results provided direct morphological and electrophysiological evidence that the adult antennae of A. fasciaticollis could function in searching for mates and host plants.     

棉铃虫雄蛾触角的毛形感器对其性信息素组分及类似物的反应

本文用单细胞电反应的记录方法,测定了棉铃虫Heliothis armigera Hubner雄蛾触角的毛形感器对其性信息素组分及雌蛾腹部提取物的反应,发现顺-11-十六碳烯醛和顺-9-十六碳烯醛能引起反应。对前者发放大脉冲,对后者发放小脉冲,对雌蛾腹部提取物发放大、小两种脉冲,但以大脉冲为主。     

Identification and localization of two sensory neuron membrane proteins from Spodoptera litura (Lepidoptera: Noctuidae)

Sensory neuron membrane proteins (SNMPs), which are located on the dendritic membrane of olfactory sensory neurons (OSNs), are proposed to be associated with odor reception in insects. Recent studies have demonstrated that SNMP1 is essential for electrophysiological responses of OSNs to the sex pheromone, cis‐vaccenyl acetate (cVA) in Drosophila melanogaster. To investigate the function of Lepidoptera SNMPs, we cloned two SNMP genes, SlituSNMP1 and SltiuSNMP2, from Spodoptera litura (Lepidoptera: Noctuidae). Sequence alignment and phylogenetic analysis showed that both genes bear the general characteristics of SNMPs, including six conserved cysteine residues and two transmembrane domains. Further expression profile experiments showed that SlituSNMP1 is mainly expressed in the antenna, while SlituSNMP2 is broadly expressed in various tissues. By in situ hybridization experiments, it was found that SlituSNMP1 expressing cells are surrounded by the SlituSNMP2 expressing cells in the pheromone sensitive sensilla, suggesting different functions of the two SNMPs in insect olfaction.     

昆虫触角感器类型及其功能研究进展

触角感器是昆虫对环境变化产生行为响应的重要基本结构单元,作为昆虫内部神经系统与外部环境进行信息交流的关键接口,受到广泛关注。由于不同环境压力的作用,长期适应性进化使昆虫触角上着生有不同类型的感器,且执行着差异化的生物学功能。触角感器在昆虫识别寄主、寻找配偶、躲避天敌等行为变化中具有重要作用,若深入理解昆虫行为变化的内在机理,则有必要清晰认识昆虫触角感器类型与潜在功能。本文对已有研究结果进行系统性综述与总结。截止目前,共发现有61种昆虫触角感器类型,且触角感器存在种内与种间特征差异。同时针对12种常见的触角感器功能进行梳理,提出昆虫触角感器未来可深入开展的研究方向。本文全面了解各昆虫触角感器类型特征和功能,为从形态结构方面进行昆虫分类研究提供新视角,也为今后从化学生态学角度深入开展昆虫行为对环境改变的适应性等研究提供科学依据。     

Glomerular targets of Heliothis subflexa male olfactory receptor neurons housed within long trichoid sensilla

We used single-sensillum recordings to characterize male Heliothis subflexa antennal olfactory receptor neuron physiology in response to compounds related to their sex pheromone. The recordings were then followed by cobalt staining in order to trace the neurons' axons to their glomerular destinations in the antennal lobe. Receptor neurons responding to the major pheromone component, (Z)-11-hexadecenal, in the first type of sensillum, type-A, projected axons to the cumulus of the macroglomerular complex (MGC). In approximately 40% of the type-A sensilla, a colocalized receptor neuron was stained that projected consistently to the posterior complex 1 (PCx1), a specific glomerulus in an 8-glomerulus complex that we call the Posterior Complex (PCx). We found that receptor neurons residing in type-B sensilla and responding to a secondary pheromone component, (Z)-9-hexadecenal, send their axons to the dorsal medial glomerulus of the MGC. As in the type-A sensilla, we found a cocompartmentalized neuron within type-B sensilla that sends its axon to a different glomerulus of the PCx4. One neuron in type-C sensilla tuned to a third pheromone component, (Z)-11-hexadecenol, and a colocalized neuron responding to (Z)-11-hexadecenyl acetate projected their axons to the anteromedial and ventromedial glomeruli of the MGC, respectively.     

昆虫信息素结合蛋白的研究概况

在昆虫感受信息素的嗅觉反应中,信息素结合蛋白发挥了重要的作用。它作为脂溶性信息素的溶剂和载体,在亲水性淋巴液中起着运载信息素和使之失活的双重作用。由于它在昆虫识别信息素物质中起着重要的作用,近1 0年来,国内外对其进行了广泛、深入的研究。文章从信息素结合蛋白的生化特点、表达情况、代谢以及生理功能等方面的概况进行综述。     

Cloning and expression pattern of a putative octopamine/tyramine receptor in antennae of the noctuid moth <Emphasis Type="Italic">Mamestra brassicae</Emphasis>

In insects, biogenic amines have been shown to play an important role in olfactory plasticity. In a first attempt to decipher the underlying molecular mechanisms, we report the molecular cloning and precise expression pattern of a newly identified octopamine/tyramine-receptor-encoding gene in the antennae of the noctuid moth Mamestra brassicae (MbraOAR/TAR). A full-length cDNA has been obtained through homology cloning in combination with rapid amplification of cDNA ends/polymerase chain reaction; the deduced protein exhibits high identities with previously identified octopamine/tyramine receptors in other moths. In situ hybridization within the antennae has revealed that MbraOAR/TAR is expressed at the bases of both pheromone-sensitive and non-sensitive olfactory sensilla and in cells with a neurone-like shape. In accordance with previous physiological studies that have revealed a role of biogenic amines in the electrical activity of the receptor neurones, our results suggest that biogenic amines (either octopamine or tyramine) target olfactory receptor neurones to modulate olfactory coding as early as the antennal level.     

利用单感器记录与神经元示踪结合对棉铃虫主要性信息素感器内神经元投射的鉴定

【目的】鉴定雄性棉铃虫Helicoverpa armigera成虫触角性信息素感器嗅觉受体神经元的功能、形态及中枢投射路径。【方法】利用单感器记录技术记录棉铃虫嗅觉受体神经元对性信息素的反应,同时采用荧光染料作为示踪剂染色标记嗅觉受体神经元;使用免疫组织化学方法处理相应的脑组织,标记脑内触角叶的神经纤维球结构;用激光扫描共聚焦显微镜获取图像数据,使用图形软件ZEN和Amira 4.1.1进行三维结构重建。【结果】记录到雄性棉铃虫成虫触角上长毛形感器对主要性信息素成分Z11-16∶Ald产生明显的电生理反应,并成功染色标记了该感器内的嗅觉受体神经元。染色标记显示该感器内具有两个嗅觉受体神经元,其轴突通过触角神经分别投射触角叶内的云状体神经纤维球和普通神经纤维球。【结论】单感器记录与神经元示踪两技术结合能够用于鉴定昆虫触角嗅觉受体神经元的功能、形态和投射至神经纤维球的路径。与赖氨酸钴方法比较,使用荧光染料法进行神经元示踪,操作更简便,且易于进行三维空间分析,为调查棉铃虫其他嗅觉神经元的投射路径以明确外周气味受体感受与中枢系统的联系提供了有力技术支持。