Table 1. Stability of the dark current during the experiment.

Species	Id NR	Id Forsk	Forsk/NR ratio
	pA	pA
Frog	30.3 ± 3.3 (10)	29.2 ± 3.9 (10)	0.95 ± 0.06 (10)
Toad	22.8 ± 1.6 (11)	20.5 ± 2.0 (11)	0.89 ± 0.06 (11)

Dark current in normal Ringer, I_{d NR}, was measured at the start of the recording. Dark current in forskolin-containing solution, I_{d Forsk}, was measured at the end of the perfusion with forskolin. Each value is mean ± SEM. The number of rods is given in parentheses. Paired t test shows no statistically significant effect of forskolin.