Pheromone Processing: Inverts

• odourant • sensilla • odourant binding protein • olfactory sensory neuron • glomeruli (connected by interneurons) • projection neurons • kenyon cells (and lateral horn)

• pheromone • sensillum • pheromone binding protein • olfactory sensory neuron • macroglomeruli complex (and glomeruli) • projection neuron • lateral horn (and kenyon cells)

• pore - 2-4 OSNs with dendrites extending up

• can have multiple pores to increase sensitivity • oily coating to prevent pore from clogging (inspired solution for nanotool that looks at single molecules) • different types which are mapped on antennal surface

• trichoid: other pheromones (hair like) • basiconic: food odours, CO2 (peg like) • coeloconic: food odours, ammonia, amines, water vapour, alcohols (recessed peg like) • ampulacea: pore plates

• needs olfactory or pheromone binding protein in order to travel through lymph • binding protein also allows for an “off-switch” as it degrades

• bind to 7 transmembrane receptor (g-protein coupled receptor) activating an iontropic and metabotropic pathway • the n-terminus of the receptor is intracellular

• OR 83B • results in fast and transient ion conductance • Na and Ca influx and membrane depolarizes

• OR 22a • results in activation of g-proteins • g-alpha subunit stimulates adenylyl cyclase which increases ATP to cAMP production • cAMP slowly activates a long lasting non-selective cation conductance (CNGCC) which causes influx of Ca and Na and causes depolarization

• so the organism can respond right away and maintain the response • cascades allow for energy/info to be translated so that the system understands • cascades allow for amplification

• 2-4 per sensilla • project to glomeruli in the antennal lobe • each glomeruli will receive multiple inputs from osns with the same receptor type • stimulus is encoded as firing rates in osns (increase in dose = increase in firing rate)

• regularly: multiple osns with same receptor converge onto glomeruli • co-convergence: osns with different receptor types converge onto same glomeruli • co-expression: osns with two receptor types converge onto same glomeruli

• glomeruli organized so that similar odours (similar chemical structure) are spatially close to one another • similarly mapped on the antennal surface by receptor type

• male-specific type of glomeruli in insects that use pheromones • receive input from sex pheromone specific osns

• by the osns converging to glomeruli (30:1)

• specificity increased via lateral inhibition by local inhibitory neurons • excitation of one glomeruli will excite an inhibitory interneuron that dampens the excitation of other glomeruli

• dorsal, anterior brain • ventral nerve cord • if ancestral: one ganglion/segment • otherwise: fusion of ganglia • subesophageal ganglion: principle centre for motor control • 2-4 pairs of lateral nerves/ganglion

• greater diversity of receptors than vertebrates • chemoreceptors: olfactory and gustatory info (humidity and osmotic) • mechanoreceptors: sensory spines/hairs, motion receptors, contact receptors, strain receptors • auditory receptors and gravitational organs • simple and compound eyes with photoreceptors and temperature receptors

• may connect with many glomeruli • use complex temporal patterning rather than rate code to respond to different odours (partly due to the inhibitory interneurons)

• projection neurons connect with either kenyon cells in the mushroom bodies or the lateral horn • information they receive may be unprocessed or processed by lateral interaction between glomeruli

• protocerebrum: optic lobes, mushroom bodies (receive sensory input and provides to the central body), central body (central pattern generator), pars intercerebalis • dentocerebrum: antennal lobes (chemosensory input), dorsal lobe (motor output) • tritocerebrum: gut activity

• important for distinguishing between odourant and pheromones • acute and innate behaviour • coarse discrimination

• important for learning, memory, integration of multisensory information and fine discrimination

• bioessays: honeybees trained to anticipate a reward when a certain stimulus is presented • electroantennograms: examine electrical signals from antennae to look at activation caused by different odours • extracellular recordings: to look at electrical activity to certain scents in alive/intact moths