Molecular Tranduction Mechanism in Chemoreception

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1 Olfactory cells were isolated from the newt and frog, and patchclamp technique was applied to them. Using whole cell-clamped cells, characteristics of the cation conductance activated by the olfactory stimuli were compared with those activated by the cyclic nucleotides. Localization at the olfactory cilia, cation selectivity and adaptation by internal Ca^<2+> were the same, indicating that the cyclic nucleotide-activated channels transduce olfactory signals. The cAMP-activated channels in the inside-out patch were not inactivated by Ca^<2+>, showing that adaptation is not a direct effect of Ca^<2+> on the channels.2 Labellar taste cells of the fleshfly were isolated from labella of the pupa 2 - 3 days before eclosion by enzymatic treatment. The labellar taste cell belonging to the sensory hair was bipolar with a sensory process and an axon and had dimension of about 8 x 15 mum. Its resting potential was about -40 - -50 mV and it generated action potentials by current injection or spontaneously at whole-cell current-clamp condition. The whole-cell voltage-clamped cells caused inward current of 20 - 80 pA in response to the pressure applied 50 mM sucrose with little latency, supporting the view that the receptor -ion channel complex directly operated by the sugar exists on the receptor membrane and tansduces sugar sensation. Second messengers such as cGMP, IP_3 and Ca^<2+> may modulate the transduction.3 Frog taste cells were isolated and whole-cell clamped. Application of acids activated cation conductance, suggesting that this conductance transduces acid taste sensation.