AN ENZYMATICALLY ENHANCED RECORDING TECHNIQUE FOR LIMULUS VENTRAL PHOTORECEPTORS - PHYSIOLOGY, BIOCHEMISTRY, AND MORPHOLOGY

Enzymatic treatments that facilitated whole-cell electrophysiological recordings were used on Limulus ventral photoreceptor cells. Ventral o ptic nerves were treated with either collagenase or collagenase, papai n, and trypsin. Either treatment greatly increased the ease of making whole-cell recordings of transmembrane potentials. Light responses obt ained from enzyme-treated photoreceptor cells were nearly identical to results obtained without enzyme treatment and compared favorably to i n vivo recordings of light responses from the compound lateral eye. En zyme-treated cells also responded to applied octopamine, as do untreat ed cells, with an increased phosphorylation of a 122-kD protein. This suggests that the external receptors and internal biochemical machiner y required for at least one second-messenger cascade are present after enzyme treatment. The morphological integrity of enzyme-treated photo receptor cells was examined with light microscopy as wen as with scann ing and transmission electron microscopy. In general, we found that ea ch enzyme treatment greatly reduced the integrity of the layers of gli al cells that surround the photoreceptor cells thereby making these ce lls easily accessible for whole-cell recordings of transmembrane poten tials. The morphology of the rhabdomere was normal after enzymatic deg radation of the adjacent glial covering.