Effect of chlorobutanol on Limulus ventral photoreceptor latency: A model of a two component latent period

Chlorobutanol (1,1,1-trichlor-2-methyl-2-propanol) decreases the duration of the latent period of Limulus ventral eye receptor potentials. This effect is both concentration and intensity dependent. Between 0.05 and 1 mM chlorobutanol in sea water the extent of latency shortening approximates a linear function of the logarithm of the chlorobutanol concentration. The latency shortening effect of chlorobutanol diminishes with decreasing intensity of stimulation and virtually disappears at intensities just exceecling threshold. These results are explained by postulating that the latent period is composed of two processes only one of which is sensitive to chlorobutanol and, further, that the duration of the chlorobutanol-sensitive process is not appreciably affected by the stimulating intensity. This model of a two component latent period may be tested experimentally. In several experiments prolonged exposure of ventral photoreceptor cells to chlorobutanol coupled with a short exposure to calcium deficient sea water produced a collapse of the receptor potential followed by a slow recovery after returning to perfusion with normal sea water. During the recovery a slow, low amplitude positive wave exists which has been tentatively called a prepotential.