0 20000 1 -0.1 1.0 68 8.5 104 0.1 2.5 3.5 4 3 2 2 4 4 4 0 0 0 2.5 2.0 2.0 0 0 20 20 20 20 2 200 cAMP 1 4 10 0.8 3 cAMP Refractoriness 0.37 0.01 1.0 0.0 8 850 750 500 0.2 cAMP