Horizontal cells and retinal ganglion cells
The research program in the Baldridge Lab involves two major themes:
Circuitry of the vertebrate retina with particular emphasis on the role of horizontal cells
Horizontal cells (HCs) are second-order neurons in the retina with large receptive-fields due to extensive electrical coupling by gap junctions. Horizontal cells are thought to modulate the first synapse of the visual system. Their large receptive-field size averages luminance levels, adjusting gain at photoreceptor synapses.
A long-standing interest in the Baldridge Lab is to characterize the modulation of gap junction coupling between HCs. We have shown that coupling is altered by the level of ambient illumination and are currently investigating the role of different known modulators of HC coupling (dopamine, nitric oxide, retinoic acid) on light-dependent changes in HC receptive-field size. We are also interested in the mechanism by which HCs influence (“feedback”) the output from photoreceptors.
Calcium dynamics of mammalian retinal ganglion cells
Retinal ganglion cells (RGCs) are the output neurons of the retina, the axons of which form the optic nerve that carries visual information to the brain. An ongoing interest in the lab is the development of protocols to visualize and quantify the level of intracellular calcium ([Ca2+]i) in mammalian RGCs using calcium imaging microscopy.
A current priority in the lab is the development of in vivo multiphoton imaging techniques to measure [Ca2+]i in RGCs. Changing levels of [Ca2+]i can be used as an indicator of RGC activity and prolonged or excessive increases of [Ca2+]i are known to cause RGC death. Therefore, by using in vivo imaging techniques, we can monitor [Ca2+]i in animal models of glaucoma and diabetic retinopathy to track the progression of these retinal diseases.
Find out more
- Daniels, B.A., L. Wood, F. Tremblay and W.H. Baldridge (2012) Functional evidence for D-serine inhibition of non-NMDA ionotropic glutamate receptors in retinal neurons. European Journal of Neuroscience. 35:56-65.
- Daniels, B.A. and W.H. Baldridge (2011) The light-induced reduction of horizontal cell receptive-field size in the goldfish retina involves nitric oxide. Visual Neuroscience. 28:137-144.
- Trenholm, S. and W.H. Baldridge (2010) The effect of aminosulfonate buffers on the feedback responses and intracellular pH of goldfish retinal horizontal cells. Journal of Neurochemistry, 115:102–111.
- Daniels, B.A. and W.H. Baldridge. (2010) D-serine enhancement of NMDA receptor-mediated calcium increases in rat retinal ganglion cells. Journal of Neurochemistry, 112:1180-1189.
- Pérez de Sevilla Müller, L., M.T.H. Do, K. Wai-Yau, S. He and W.H. Baldridge (2010) Tracer coupling of intrinsically photosensitive retinal ganglion cells in the mouse retina. Journal of Comparative Neurology, 518:4813-4824.
A large part of the funding for the Baldridge Lab comes from:
- Natural Sciences and Engineering Research Council of Canada
- Canadian Glaucoma Society
- Atlantic Innovation Fund (Co-applicant, PI B. Chauhan)
|Dr. Michael Davis||MSc||2001||Physician, Nova Scotia|
|Dr. Anna Stratis||MSc||2003||Physician, India|
|Dr. Andrew Hartwick||PhD||2006||Associate professor, Ohio State University|
|Dr. Bryan Daniels||MSc
|Postdoc, McGill University|
|Dr. Jianing Yu||MSc||2006||Postdoc, Janelia Farm|
|Ds. Claire Hamilton||MSc||2007||Ophthalmology resident, Dalhousie University|
|Dr. Stuart Trenholm||MSc||2009||Postdoc, Freidrich Meisner Institute, Switzerland|
|Ms. Sahira Husain||MSc||2012||Orthoptist, Ontario|
|Dr. Luis Perez de Sevilla Müller||Postdoctoral fellow||2008-2011||Research associate, University of California, Los Angeles|