Desensitization to gamma-aminobutyric acid (GABA) was demonstrated in crab muscle fibres by measurements to conductance changes induced by the drug. 2. In standard solutions (containing 34 mM-Ca2+), complete desensitization occurred in the presence of 5 X 10(-4) M-GABA. In Ca2+-free solutions, however, only partial (70-80%) desensitization was observed after the application of the same concentration of GABA. 3. Complete recovery of the membrane sensitivity to GABA was achieved after less than 60 min of continuous washout with standard solution. Only partial (10%) recovery was observed after 1 hr of washout with Ca2+-free solution. 4. The results support the 'receptor hypothesis' of desensitization which assumes transformation of the receptor from an effective to refractory state, as opposed to the 'ionophore hypothesis' which assumes direct inactivation of the synaptic current. 5. The possible mechanism by which Ca ions effect desensitization is discussed in terms of the 'cyclic model' of Katz & Thesleff (1957).
摘要
通过测量药物诱导的电导变化，在蟹肌纤维中证实了对γ-氨基丁酸（GABA）的脱敏作用。2. 在标准溶液（含34 mM - Ca2+）中，5×10(-4) M - GABA会导致完全脱敏。然而，在无Ca2+溶液中，施加相同浓度的GABA后仅观察到部分（70 - 80%）脱敏。3. 用标准溶液连续洗脱不到60分钟后，膜对GABA的敏感性完全恢复。用无Ca2+溶液洗脱1小时后仅观察到部分（10%）恢复。4. 这些结果支持脱敏的“受体假说”，该假说假定受体从有效状态转变为不应状态，这与假定突触电流直接失活的“离子载体假说”相反。5. 根据Katz和Thesleff（1957年）的“循环模型”讨论了钙离子影响脱敏作用的可能机制。
