Response enhancement of olfactory sensory neurons-based biosensors for odorant detection

This paper presents a novel strategy for the response enhancement of olfactory sensory neurons (OSNs)-based biosensors by monitoring the enhancive responses of OSNs to odorants. An OSNs-based biosensor was developed on the basis of the light addressable potentiometric sensor (LAPS), in which rat OSNs were cultured on the surface of LAPS chip and served as sensing elements. LY294002, the specific inhibitor of phosphatidylinositol 3-kinase (PI3K), was used to enhance the responses of OSNs to odorants. The responses of OSNs to odorants with and without the treatment of LY294002 were recorded by LAPS. The results show that the enhancive effect of LY294002 was recorded efficiently by LAPS and the responses of this OSNs-LAPS hybrid biosensor were enhanced by LY294002 by about 1.5-fold. We conclude that this method can enhance the responses of OSNs-LAPS hybrid biosensors, which may provide a novel strategy for the bioelectrical signal monitor of OSNs in biosensors. It is also suggested that this strategy may be applicable to other kinds of OSNs-based biosensors for cellular activity detection, such as microelectrode array (MEA) and field effect transistor (FET).

Loss of CO_2 sensing by the olfactory system of CNGA3 knockout mice

Atmospheric CO2 can signal the presence of food, predators or environmental stress and trigger stereotypical behaviors in both vertebrates and invertebrates. Recent studies have shown that the necklace olfactory system in mice sensitively detects CO2 in the air. Olfactory CO2 neurons are believed to rely on cyclic gnanosine monophosphate （cGMP） as the key second messenger; however, the specific ion channel underlying CO2 responses remains unclear. Here we show that CO2-evoked neuronal and behavioral responses require cyclic nucleotide-gated （CNG） channels consisting of the CNGA3 subunit. Through Ca2＋-imaging, we found that CO2-triggered Ca2＋ influx was abolished in necklace olfactory sensory neurons （OSNs） of CNGA3-knockout mice. Olfactory detection tests using a Go/No-go paradigm showed that these knockout mice failed to detect 0.5% CO2. Thus, sensitive detection of atmospheric CO2 depends on the function of CNG channels consisting of the CNGA3 subunit in necklace OSNs. These data support the important role of the necklace olfactory system in CO2 sensing and extend our understanding of the signal transduction pathway mediating CO2 detection in mammals [Current Zoology 56 （6）： 793-799, 2010].

Glomerular organization in the antennal lobe of the oriental armyworm Mythimna separata

In insects,the number and specificity of antennal lobe glomeruli often reflect the number and diversity of expressed chemosensory genes,which are linked to its ecological niche and specific olfactory needs.The oriental armyworm,Mythimna separata,is an important and common lepidopteran pest of cereal crops.Given its reliance on the olfactory system for crucial behaviors,understanding the evolutionary potential of this system requires a thorough characterization of the anatomical structure of the primary olfactory center.Here,we systematically identified all antennal lobe glomeruli of M.separata based on synaptic antibody immunostaining and mass staining of the olfactory sensory neurons.A total of 69 glomeruli were identified in females and 65 in males,and an intuitive nomenclature based on glomerular positions was applied.Our findings uncovered some sex-specific glomeruli in this species.There were ten female-specific glomeruli and three male-specific glomeruli,except for the macroglomerular complex(MGC)units,with a notable observation that the female labial pit organ glomerulus was larger than its male counterpart.Additionally,we identified four antennal-lobe tracts(ALTs)and retrograde labeling from the calyx revealed that all glomeruli were innervated by the medial ALT projection neurons.The comparison of the olfactory system structures between M.separata and sympatric moths supports their evolutionary convergence in noctuid moths.These results collectively lay the foundation for future studies on olfactory processing in M.separata.

Functional map of the macroglomerular complex of male Helicoverpaarmigera

The mechanism of sex pheromone reception in the male cotton bollworm Helicoverpa armigera has been extensively studied because it has become an important model system for understanding insect olfaction.However,the pathways of pheromone processing from the antenna to the primary olfactory center in H.armigera have not yet been clarified.Here,the physiology and morphology of male H.armigera olfactory sensory neurons(OSNs)were studied using single sensillum recording along with anterograde filling and intracellular recording with retrograde filling.OSNs localized in type A sensilla responded to the major pheromone component cis-11-hexadecenal,and the axonal terminals projected to the cumulus(Cu)of the macroglomerular complex(MGC).The OSNs in type B sensilla respondcd to the bchavioral antagonist cis-9-tetradecenal,and the axonal terminals projected to the dorsomedial anterior(DMA)unit of the MGC.In type C sensilla,there were 2 OSNs:one that responded to cis-9-tetradecenal and cis-11-hexadecenol with the axonal terminals projecting to the DMA,and another that responded to the secondary pheromone components cis-9-hexadecenal and cis-9-tetradecenal with the axonal terminals projecting to the dorsomedial posterior(DMP)unit of the MGC.Type A and type B sensilla also housed the secondary OSNs,which were silent neurons with axonal terminals projected to the glomerulus G49 and DMP.Overall,the neural pathways that carry information on attractiveness and aversiveness in response to female pheromone components in H.armigera exhibit distinct projections to the MGC units.