Studies on the role of calcium in adaptation of the crustacean stretch receptor. Effects of intracellular injection of calcium, EGTA and TEA.

The effects of intracellular pressure injection of Ca2+, EGTA and TEA on the receptor potential of the crayfish stretch receptor were studied. Injection of Ca2+ caused both the transient phase and the static phase of the receptor response to diminish in amplitude, the decrease being greater for the static phase. This phase was almost abolished after a few minutes of injection. Injection of EGTA caused a decrease in the amplitude of the transient phase and an increase of the static phase. These changes progressed during the injection and finally the receptor potential became almost square. After injection of TEA the static phase increased and approached the height of the transient phase making the response almost square. The results provide evidence for the important role of intracellular Ca2+ for the adaptation of the receptor. It is suggested that the adaptive decline of the receptor potential is due to an outward potassium current which is controlled by the intracellular concentration of Ca2+.