The ventral photoreceptor of Limulus continues to be a highly productive preparation for detailed electrophysiological studies of phototransduction and light-adaptation: it is large, isolated, and readily voltage-clamped. This research will reveal new evidence that: (i) ventral photoreceptors (in situ) undergo circadian changes in responsivity to light; and (ii) pharmacological agents, shown to mimic the effects of endogenous efferent neurotransmission in the lateral eye, change function in ventral photoreceptors as well. These findings open up the possibility for uncovering the mechanisms mediating efferent control of photoreceptor gain (change in membrane conductance per photon), shape or duration of quantal bumps, and other cellular mechanisms associated with phototransduction or light-adaptation that are under efferent control.
