My laboratory combines electrical, optical, and molecular biology techniques to study mechanisms of synaptic transmission. In recent years two subjects have been of interest: 1) control of synaptic transmitter vesicle cycling, and 2) the function of transporters that move synaptic transmitter molecules across membranes. Both subjects have been studied at synapses between identified retinal cells. Fortunately, the detailed anatomy of the retina is well known and its cells are readily accessible. This allows us to study recognized synapses and complete experiments that would be more difficult in other brain areas. 

The control of vesicle cycling has been studied both in situ and with solitary cells. Transmission between identified cells is being studied in a retinal slice. The pre-synaptic voltage is controlled and the post-synaptic current recorded in order to measure the transfer of a signal across a single synapse. The results can be used to determine the kinetics of synaptic vesicle mobilization and cycling. Complimentary studies come from the study of solitary cells. Two types of retinal neuron have large synaptic terminals (5-10 µM diameter) that permit direct optical and electrical measurement. Recent experiments have revealed a novel pathway for Ca²⁺ to enter a terminal, the Ca²⁺ dependence of synaptic vesicle cycling, and how an individual synapse can switch from continuous to transient transmitter release as the pre-synaptic signal is changed. 

Transporters are proteins that move transmitters in both directions across cell membranes. In most neurons, transporters move transmitter molecules into a cell and function to recapture or uptake transmitter after release. However, in some neurons transporters also operate in the opposite direction and function in the release of transmitter. Voltage controls the balance between uptake and release. Experiments on native and cloned transporters are now designed to reveal the exact mechanism of how a transporter protein moves a transmitter molecule across a membrane.