Chemo-electrical transduction in insect olfactory receptors.

Abstract

Insect behavior can be controlled by a single odor 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