Receptor mechanisms for flavour stimuli

Abstract

The perception of flavour is the result of complex processing of sensory signals that initiate from the periphery and terminate in the central nervous system. The receptor mechanisms operative in chemosensory signal transduction are varied in type and specificity. Transduction of taste stimuli involves a number of receptor and cellular mechanisms including passage of stimuli through receptor cell ion channels, blockage of ion channels, receptor-mediated changes in intracellular second messengers and the activation of stimulus-gated ion channels. These mechanisms impart specificity to the process of taste transduction and result in neurotransmitter secretion that alters firing of innervating sensory nerves. Transduction of olfactory stimuli also involves a number of mechanisms. A large family of olfactory receptors has been cloned. These receptors are linked via GTP-binding regulatory proteins to production of second messengers, including cyclic AMP and/or inositol trisphosphate. These second messengers directly gate ion channels which allow influx of cations to depolarize the olfactory receptor neuron. There is also evidence for stimulus-gated ion channels in olfactory signal transduction. The transduction processes for chemesthesis (somatosensory chemoreception carried primarily by the trigeminal nerve) are not well understood, but may involve both specific receptor processes and purely physico-chemical ones. Integration of these mechanisms from multiple stimuli through these multiple sensory systems leads ultimately to flavour impressions.