Synaptic lamellae of the photoreceptors of pearl and wild-type mice.

The retina of the pearl mutant mouse, C57BL/6J pe/pe, exhibits reduced light sensitivity in the dark-adapted condition (Balkema and Pinto, J Neurophysiol 48:968, 1982). The authors searched for an anatomic correlate in the retina which could relate to the functional deficit. Electron microscopic mosaics of the outer plexiform layer of light- and dark-adapted pearl and wild-type mice were analyzed. The numerical density and length of the photoreceptor synaptic lamellae showed these parameters to be indistinguishable in wild-type and pearl retinas under conditions of both light- and dark-adaptation. Light-adapted pearl retinas exhibited some rod spherules that contained structurally modified synaptic lamellae with bulbous thickenings and adjacent electron-dense bodies. These lamellar modifications were neither apparent in the light-adapted, wild-type retinas, nor in the dark-adapted retinas of either genotype. Pronase application to ultrathin sections hydrolyzed synaptic lamellae, bulbous thickenings and electron dense bodies.