Chemo-Electrical Transduction in Insect Olfactory Receptors

Abstract

INTRODUCTIONInsect behavior can be controlled by a single odor compound or by a blend of a few components in an exact ratio of concentrations. These odor compounds or odor mixtures are called pheromones if used for intraspecific communication. Each of the pheromone components is perceived by a particular type of receptor cell that is specifically tuned to its "key compound" and may respond to single odor molecules by firing single nerve impulses. The entire response range of a receptor cell may cover many decades of stimulus intensities. Each olfactory receptor cell is a bipolar neuron. Its dendrite innervates a specialized cuticular structure, usually a hollow cuticular hair that captures the stimulus molecules. The axon runs directly to the deutocerebrum-the first synaptic relay station of the central nervous system.Chemo-electrical transduction in these organs comprises the processes leading from the adsorption of odor molecules on the cuticular surface via stimulus transport to the generation of receptor potentials and nerve impulses and, eventually, to the inactivation of the stimulus molecules. The interconnections of these processes and their influences on the ultimate impulse response of the receptor cells are largely unknown. This review covers electrophysiological investigations of cellular response charac teristics as well as biophysical and biochemical work, much of which is based on radiolabeled pheromone compounds. These studies employed a few species of insects, mainly of moths with olfactory organs that are relatively large and accessible for experimental work. The olfactory hairs of 121

Snmp-1, a Novel Membrane Protein of Olfactory Neurons of the Silk Moth Antheraea polyphemus with Homology to the CD36 Family of Membrane Proteins

“…This is particularly curious because there are typically two or three neurons present in each sensillum, all closely related, having derived from a common sensory mother cell (34). Furthermore, each neuron differs in its response to specific pheromone components (3,41,42). The staining of only one neuron per sensillum may indicate that Snmp-1 is a molecular marker of that sibling neuron, thus suggesting some unique role for that neuron.…”

“…The antennae of silk moths are well known for their exquisite sensitivity to pheremonal odorants (1)(2)(3). Early reports demonstrated that the males of the wild silk moth Samia cynthia could locate a sex pheromone source over 2 miles away within several hours of their release (4).…”

Characterization and cDNA cloning of the pheromone-binding protein from the tobacco hornworm, Manduca sexta: a tissue-specific developmentally regulated protein.

“…These sensilla are hollow cuticular structures containing the receptor cell sensory dendrites (cilia) bathed in a fluid, called the sensillum lymph. Pheromone molecules are thought to diffuse through the pore tubules in the cuticular wall and across the sensillum lymph to reach receptors located in the cilia (3)(4)(5).…”

“…This finding and the protein's enormous 10 mM concentration in the sensillum lymph led to the suggestion that it serves to solubilize the extremely hydrophobic pheromone molecules (3)(4)(5)(6)(7).…”

Enhanced processing in arrays of optimally tuned nonlinear biomimetic sensors: A coupling-mediated Ringelmann effect and its dynamical mitigation

“…As examples, the human eye is able to count single photons [1], hair cells in the cat cochlea are able to detect displacements of the basilar membrane smaller than 10 −10 m [1], the olfactory system of the domesticated silk moth (Bombyx mori) can detect single molecules of pheromone [2], and thermal receptors in crotalid snakes are able to recognize the temperature difference of 0.003 o C [3]. All these systems share a simple design principle based on sensor array architectures; high sensitivity is achieved through the use of a large number of sensory receptors.…”