RESPONSES TO LIGHT GENERATED IN THE PRESYNAPTIC TERMINALS OF BARNACLE PHOTORECEPTORS

When the axons of barnacle photoreceptors are severed, thereby isolating the presynaptic terminal membrane from the rhabdomeric membrane, voltage changes in response to bright light can be recorded from the photoreceptor axon stumps near the presynaptic release sites. The light responses recorded from stumps were predominantly hyperpolarizing and were dependent on light intensity. Recordings from postsynaptic cells indicate that transmitter is released from the stumps during the light stimulus even though the cell hyperpolarizes.