Research InterestsThe mechanism of information transfer between neurons with particular focus on the function of the presynaptic nerve terminal. The direct examination of presynaptic ion channel activity and its relation to transmitter release.
Canada Research Chair
Senior Scientist, Toronto Western Research Institute, UHN
Professor, Depatment of Physiology, University of Toronto
Supervisor Wright Cellular Imaging Facility
Keywords: Synaptic Transmission /Cellular Electrophysiology / Calcium channels / Patch-Clamp / Electrophysiology / Immunocytochemistry / Cellular Neurobiology / biochemistry / presynaptic / active zone
Transmission of impulses from one neuron to another occurs mostly at chemical synapses, points of close membrane apposition. At these sites action potentials trigger the release of neurotransmitter from specialized sites at the presynaptic terminal trigger which diffuses across the synaptic cleft to activate the postsynaptic neuron. While the postsynaptic events in this process are relatively well understood, the presynaptic ones remain something of a mystery. This is largely due to the small size of these structures (~2 micron diameter) that generally precludes direct experimentation with electrophysiological techniques. In 1989 we demonstrated that it was possible to use a calyx-type synapse from the chick ciliary ganglion to record directly from a presynaptic nerve terminal using patch clamp techniques. We have used this preparation to achieve a number of firsts: the recording and characterization of a calcium current in a vertebrate presynaptic nerve terminal (1989-91); the recording of calcium channels at the single channel level from a transmitter release site (1991,3); the direct correlation of single calcium channel activity with the quantal release of neurotransmitter (1993), the structural localization of presynaptic calcium channels at nanometer resolution (1994), direct biophysical characterization of a presynaptic ligand-gated receptor (for ATP 1996) and characterization of presynaptic calcium-activated potassium channels at the single channel level (1999). In 1997 we presented evidence suggesting that there is a link between the secretory role of the presynaptic calcium channel and the G protein-dependent modulation of this channel via G proteins. Recent reports include the direct measurement of single calcium channel calcium ion conductance with physiological ion concentrations and prediction of the intracellular functional architecture at the release site.
Cell and tissue culture: Neurons, dorsal root ganglion, primary neurons.
Procedures: Electrophysiology, immunocytochemistry, in-vitro electrophysiology, patch clamp, proteomics, voltage clamp, western blot, immunoprecipitation, fusion proteins.
Amplifier, analytical balances, benchtop centrifuge, calcium imaging system, culture hood, culture incubators, deconvolution fluorescence microscope, digital microscope, dissecting microscope, electrophysiology rig, fluorescence microscope, fresh tissue sectioning systems, gel apparatus, low- and high-speed centrifuge, micropipette puller.
Sabiha GardeziFiona Wong
Gabriella RoaznskiArup Nath
Within the Department of Physiology:
Publications and Awards