Dal Alert!

Receive alerts from Dalhousie by text message.


Baldridge Lab

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.

Learn more about our multiphoton imaging project.

Find out more



A large part of the funding for the Baldridge Lab comes from:

Former trainees

Trainee Degree Year Current position
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