A reweighting of receptor mechanisms in the ground squirrel retina: PIII and B-wave spectral sensitivity functions.

PIII and b-wave spectral sensitivity functions were measured under various adapted conditions in the 13-lined ground squirrel. The PIII was isolated by intravitreal injection of sodium L-aspartate. Under the conditions studied, the PIII spectral sensitivity function always fitted the absorption spectrum of a 518 +/- 3 mm Dartnall nomogram. This suggests that of the three photoreceptors ('rod-like', 'blue' cone and 'green' cone) present in the 13-lined ground squirrel the green cones are the overwhelming majority. The dark-adapted b-wave had two components; a b1-wave with a spectral sensitivity that fitted a 516 +/- 1 nm Dartnall nomogram and a b2-wave with a spectral sensitivity that fitted a 502 +/- 4 nm Dartnall nomogram. The light-adapted b-wave had a spectral sensitivity that fitted a 516 +/- 2 nm Dartnall nomogram.