In order to account for the multi-phasic dynamics of photopigment regeneration in human rods, we developed a new model of the retinoid cycle. We first examined the relative roles of the classical and channeling mechanisms of metarhodopsin decay in establishing these dynamics. We showed that neither of these mechanisms alone, nor a linear combination of the two, can adequately account for the dy...

The elementary responses, the “bumps”, o f the ventral photoreceptor o f Limulus polyphemus were studied under voltage clamp conditions. We compared sponta­ neous bumps with those induced by light and we applied the G-protein activator A1F4. The amplitude o f the spontaneous bumps is on the average 7 8 times smaller than that o f the light-induced bumps. Bumps induced by A1F4_ have identical si...

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 a...

Phototransduction in flies is the fastest known G protein-coupled signaling cascade, but how this performance is achieved remains unclear. Here, we investigate the mechanism and role of rhodopsin inactivation. We determined the lifetime of activated rhodopsin (metarhodopsin = M( *)) in whole-cell recordings from Drosophila photoreceptors by measuring the time window within which inactivating M(...

We have recently demonstated the dissection of the transduction process in the barnacle photoreceptor into antagonistic "excitor" and "inhibitor" processes. We now show that (a) the interaction between the two processes proceeds even when they are induced in different pigment molecules; (b) the excitor process appears to be slightly facilitated if those pigment molecular unaffected by the stimu...