Responses of barnacle photoreceptors to high energy flashes of short duration

In chromatic adapted barnacle median and lateral photoreceptors the two stable states of the photopigment (rhodopsin R and metarhodopsin M) were interconverted with intense, colored light flashes of 1 ms duration. Only after conversion of the red adapted photoreceptor in K+-Ringer solution with an intense flash the negative early receptor potential, ERP (of R) gradually appeared detected with an indicator flash. For the opposite conversion (blue adapted, R leads M) the gradual appearance of the positive ERP (M) was not measurable in the same time span. In artificial seawater all flash stimuli yielded--irrespective of color--the transient component of the late receptor potential (LRP). ERP results for the lateral photoreceptor are discussed in view of an existing kinetic model and an attempt is made to give an explanation which covers the new LRP transient and ERP results for both types of photoreceptor (appendix).