[The role of active ion transport in the generation of the receptor potential of isolated frog muscle spindles].

Effects of lithium ions and ouabain on the receptor potential were studied in an isolated frog muscle spindle. Lithium ions and ouabain caused a reduction and rapid disappearance of the hyperpolarization phase of the receptor potential. The dynamic and static phases of the response were less reduced. The rate of rise of the receptor potential in the Ringer lithium solution decreased. There were no changes in the characteristic deviation of the response from the dynamic peak to the static level in the Ringer solution with ouabain and in the lithium Ringer solution. The results show that fast adaptation in the isolated frog muscle spindle is not due to the activity of an electrogenic sodium pump.