Nociceptin Signaling Involves a Calcium-Based Depolarization in Tetrahymena thermophila

Figure 3

Nociceptin-NH2 is a depolarizing signal in Tetrahymena thermophila. (a) 5 μM nociceptin-NH2 causes a depolarization of approximately 20 mV, though this concentration does not often provoke a behavioral response in Tetrahymena. (b) 50 μM nociceptin-NH2 causes a depolarization of approximately 40 mV. This concentration is the EC₁₀₀ for behavioral avoidance in Tetrahymena. (c) The depolarization produced by 50 μM nociceptin-NH2 is eliminated by the addition of 1 mM EGTA to the external medium, implying that calcium is involved in the depolarization.

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(b)

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