ABSTRACT
The role of the crustacean octapeptide red pigment concentrating hormone (RPCH) in the control of crayfish retinal activity was explored. RPCH injection into intact animals resulted, after a latency of 10–30 min, in a dose-dependent enhancement of electroretinogram (ERG) amplitude lasting 60–120 min.
RPCH was able to potentiate ERG amplitude in both light-adapted and dark-adapted animals. Following light-adaptation, responsiveness to RPCH was five times higher than following dark-adaptation.
In conjunction with ERG enhancement, in light-adapted animals, RPCH injection elicited a dose-dependent retraction of distal retinal pigment, but did not affect proximal retinal pigment position.
The effects of RPCH were blocked by a polyclonal antibody raised against a tyrosinated form of RPCH (A-tyr-RPCH). The antibody was also capable of partially blocking the nocturnal phase of the circadian rhythm of ERG amplitude and the darkness-induced retraction of distal retinal pigment.
These results suggest that RPCH acts both on the retinal photoreceptors and on the distal pigment cells, playing a physiological role as a mediator of the effects induced by darkness and by the nocturnal phase of the circadian rhythm.
