Thirteenth Congress of the European Chemoreception Research Organisation

1999 Chemical Senses  
The olfactory organ of lobsters, as many other invertebrates, consists of sensilla. Each lobster olfactory sensillum contains~350 primary bipolar receptor cells, each cell of which gives rise tõ 25 outer dendritic segment (cilia). This highly enriched, highly polarized source of olfactory receptor cells facilitates localizing putative intracellular signaling pathways to the ciliary transduction compartment. Recent molecular evidence complements biochemical and electrophysiological evidence
more » ... ifying the major components of a phosphoinositide signaling pathway in the cilia. Odors activate a PLC through a G-protein coupled receptor that targets an IP3 receptor in the plasma membrane. The IP3 receptor is a functional, non-selective cation channel; activation of this pathway excites the cell. Activation appears to be a two-step process that involves secondary activation of a predominantly current-carrying channel, as is being considered for the calciumactivated chloride current in vertebrate olfactory receptor cells. In the lobster, however, secondary activation involves a novel sodium-activated, non-selective cation channel that couples to the second-messenger signaling pathway by an as yet unknown mechanism. The phosphoinositide pathway works not in place of, but rather in addition to, a cyclic nucleotide signaling pathway. In the lobster, odors activate adenylyl cyclase through a different G-protein from the one associated with phosphoinositide signaling. The cyclic nucleotide pathway appears to target a potassium channel that inhibits the cell with the same kinetics as does IP 3 -mediated excitation. The ability to modulate excitation through a parallel inhibitory pathway, i.e. to provide bipolar input, provides a functional rationale for having two olfactory second messengers. Complexity in intracellular signaling confers upon lobster olfactory receptor cells the potential to carefully regulate, and most likely integrate, the signal they transmit to the central nervous system. among the threshold values measured for two butenilydene derivatives. The influence of an alkylic substituent on the cycloalkane ring was also studied. Data show that steric hindrance near a double bond reduces the intensity of the odor. It appears that the size of rings having the same side chains deeply affects the odor. Open chain compounds and polycyclic structures containing a dienic conjugated system were synthesized in order to highlight the effect on odor of the molecule features (rigidity or flexibility). Convergence of the subfamily signatures in the honeybee colony that wing cells express functional ASSCs similar to those in frog TRCs (Avenet and Lindemann, 1988, J. Membr. Biol., 105: 245). However, we now report that in wing cells, Ki for amiloride is an order of magnitude higher (2.9 µM) than in TRCs (0.2-0.3 µM). These findings suggest that the different types of cells in a taste organ can express functional ASSCs with different properties, such as the sensitivity to amiloride. Future directions will be to determine the localization of ASSCs in the membrane (apical/ basolateral) of wing cells. The role of olfaction in mother pup recognition in big brown bats, Eptesicus fuscus Female big brown bats (Eptesicus fuscus) from the eastern USA roost in maternity colonies during the summer and give birth to two pups. During the lactation period, a female leaves her pups in the roost while she forages and then must return and suckle her own offspring. Dual choice experiments were conducted to test whether lactating females can discriminate between the odors of their own offspring and same-aged foreign pups. Female big brown bats preferentially chose the scent of their own pups over unrelated individuals. However, using olfaction alone, young pups were unable to consistently discriminate between their mothers and a foreign female. As lactation is an energetically costly process, selection may favor females that use a number of cues, including olfaction, for offspring identification and thereby avoid allocation of valuable resources to unrelated individuals. Modulation of chorda tympani sensitivity with repeated exposure to 'novel' tastants. Acute and long-term familiarization The aim of the study was to look for an eventual modulation of chorda tympani peripheral response to taste stimuli with repeated exposure to novel tastants. Three groups of 10 hamsters (Mesocricetus auratus) were exposed to novel tastants: dulcine (DUL), potassium glutamate 50 mM (KG5) and guanosine 5′monophosphate (5′-GMP), as over night two bottle tests during 15 days, prior to whole nerve chorda tympani electrophysiological recording. Two groups were not familiarized to any tastant: a control group had only water in the double bottle test, the other group received a tongue rinse with 5′-GMP 20 min before electrophysiological recording. We recorded the gustatory nerve responses to 21 stimuli repeated six times which corresponds to a 3 h experiment. Response amplitudes for the control group increased significantly for all stimuli between stimulations 1 and 6. On the contrary, CT response amplitudes of groups exposed to, and hence familiarized with, novel tastants did not increase specifically for the familiar stimulus in any case: a modulation of CT sensitivity was observed due to familiarization. In some cases, familiarization also induced changes in response amplitudes to other stimuli (generalization). For example, the group exposed to 5′-GMP generalized this effect to sodium chloride and all stimuli including glutamate anion. On the other hand, we could not observe the reciprocal effect for the group exposed to glutamate. The effect is relatively specific as familiarization to dulcin (sucrose-like to the hamster) did not generalize to sucrose. Results are discussed in terms of two hypotheses inductibility of chemoreceptor synthesis (c-fos expression) or transductional coupling facilitatation. Organization of the subependymal layer in the postnatal rat Previous attempts at defining the structure of human olfactory space have yielded contradictory results. For example, the Jeltema and Southwick (1986, J. Sens. Stud., 1: 123-136) factor analysis of 146 descriptors performed on 415 profiles (data unfortunately unpublished) gave rise to a rather cumbersome 17-dimensional space explaining 89% of the variance. Other studies based on perfumery classification systems such as the Discodor of Haarman and Reimer (1979), the rosace of Firmenich (1989) and 37. Two novel members of OBP family identified in the honeybee: sexual dimorphism and development studies
doi:10.1093/chemse/24.1.47 fatcat:3zup66wqjjbvhaysv6ym3gehse