Molecular Tranduction Mechanism in Chemoreception

1分离了蝾螈和青蛙的嗅觉细胞，并应用膜片钳技术对其进行了处理。利用全细胞夹紧的细胞，比较了嗅觉刺激激活的阳离子电导特征与环核苷酸激活的阳离子电导特征。嗅觉纤毛的定位、阳离子选择性和内部Ca^<2+>的适应是相同的，表明环核苷酸激活的通道传递嗅觉信号。Ca^<2+>并没有使camp激活的通道失活，这表明适应性不是Ca^<2+>对通道的直接影响在羽化前2 ~ 3天，用酶处理方法从蛹的唇瓣中分离出肉蝇的唇瓣味觉细胞。属于感觉毛的唇瓣味觉细胞为双极性，具有一个感觉突和一个轴突，尺寸约为8 × 15微米。静息电位约为-40 ~ -50 mV，通过电流注入或在全细胞电流箝位状态下自发产生动作电位。全细胞电压箝制细胞对施加50mm蔗糖的压力产生20 - 80pa的内向电流，潜伏期小，支持糖直接操作的受体离子通道复合物存在于受体膜上并传递糖感的观点。第二信使如cGMP， IP_3和Ca^<2+>可能调节转导分离青蛙味觉细胞并夹住整个细胞。酸的应用激活了阳离子电导，表明这种电导可以传导酸的味觉感觉。

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.