Light does not induce an increase in cyclic-GMP content of squid or Limulus photoreceptors

Both slices of squid (Loligo) retinas and Limulus ventral photoreceptors, with or without prior stimulation by flashes of bright light, were rapidly frozen and analysed for cyclic-GMP content by radioimmunoassay. Measurement of the freezing process indicated that freezing occurred at about 100 msec after the light flash. No significant changes in cyclic-GMP content were induced by light in either tissue. These data do not confirm previous reports that cyclic-GMP content of invertebrate photoreceptors is markedly increased by illumination.