Fig. 6.
Rod- and cone-driven b-waves are present in the electroretinogram of Gαo2 null mouse but absent from the Gαo1 null mouse. A, Animals dark adapted for 2 hr were stimulated with dim flashes that elicited a rod-driven, corneal-positive b-wave in the wild-type mouse and in Gαo2 null but not in the Gαo1 null. Flash intensities estimated as photoisomerizations (R*) per rod (Φ), and number of responses (n) averaged for each trace were as follows: Φ = 9; n = 18. B, Dark-adapted animals were stimulated with an intense flash isomerizing ∼0.1% of the rhodopsin. This elicited in wild-type and Gαo2 null mice a negative a-wave (shading), followed by a positive b-wave. The Gαo1 null mice showed an a-wave (although somewhat reduced) but no b-wave. Φ = 105;n = 4. C, Mice were adapted to a background (white light, 9100 R* rod−1 sec−1) that completely suppressed the rod cGMP-activated current. Rods were then stimulated with an intense white flash that isomerized ∼0.4% of the M-cone pigment and 0.03% of the UV-cone pigment. All of the animals showed a cone-driven a-wave. A typical cone-driven b-wave (positive-going response with superimposed oscillations, peaking ∼70–90 msec after the flash) was present in wild-type and αo2 null mice but was absent in the Gαo1 null animals. For all of the records, n = 16. KO, Knock-out;WT, wild type.