Effects of intracellular TEA injection on early adaptation of crustacean stretch receptor.

The effects of intracellular injection of TEA on the stretch-induced response of the slowly adapting stretch receptor of the crayfish have been examined to determine the contribution of an outward potassium current to the early adaptation of the neuron. Intracellular recording techniques including potential clamp measurements of membrane currents have been used. Injection of small amounts of TEA caused a pronounced depolarization of the neuron. In the early stage of depolarization there was a marked increase of the static phase of the response while the dynamic phase remained unchanged. When the resting membrane potential was kept constant by current injection both the dynamic phase and the static phase increased. However, the increase of the static phase was more pronounced than that of the dynamic phase and as a result the early phase of adaptation was almost abolished. Following TEA injection the reversal potential for both the dynamic phase and the static phase of the receptor current became somewhat more positive. TEA injection also reduced the outward current induced by a depolarizing potential step. The present results provide additional support for the hypothesis that the early phase of adaptation of the crustacean stretch receptor is attributed mainly to an outward potassium current.