Our laboratory is primarily interested in synaptic physiology which results in a wide diversity of projects and opportunities for trainees with a variety of interests and experience. For all our work we combine a variety of electrophysiological and optical techniques. These include whole cell patch clamp, sharp microelectrode and field potential recordings combined with widefield CCD and 2-photon laser scanning imaging and photomultiplier based spot measurements, mostly using Ca2+ indicator dyes. We run a pair of two 2-photon microscopes of one laser, suitable for in vivo imaging and electrophysiology in small animals (rats, mice and frogs) and for mammalian brain slice and isolated frog/turtle brains. Other than the lasers, these apparatus were built from scratch using old car parts and stuff I "found" in the garbage cans at Bell labs two decades ago. A bit of an exaggeration but they are definitely "home-made". A flexible 2-photon imaging program that coordinates acquisition of optical and electrophysiological signals was written entirely by Dr. James Boyd working our lab using Igor (Wavemetrics) and C++. (Jamie is currently employed with Tim Murphy's group at UBC.) and has many anatomical and quantitative analysis features. Many thanks are due to David Kleinfeld at UCSD for some key electronics circuits and technical help along the way, and of course Herr Dr. Winfried Denk who taught me not to bring my head down to tabletop level when the laser is on by cuffing me severely about the ears and yelling "nein dum...pf".
We are fortunate to have strong collaborative ties to researchers at the University of British Columbia. Tim Murphy (UBC, Psychiatry) and I have been working together closely for several years through a combined interest in synaptic physiology and functional imaging using 2-photon microscopy. A degree-granting, Graduate Program in Neuroscience Neuroscience Graduate Program was started in Sept. 2010 comprised of faculty and trainees from the Depts. of Biology, Psychology, Biochemistry and Microbiology, Physical Education and the Division of Medical Sciences. Hosted by the Division of Medical Sciences it is a cross departmental program with subgroups (cellular, cognitive, exercise) in different departments.
Our work is primarily supported by operating grants from NSERC and CIHR and the International Rett Sydrome Foundation. The interface between our CIHR and NSERC research programs develops from the concept that the processing of information by neural networks can be modified by activity and modulator dependent changes in synaptic connections. We study basic properties of synaptic transmission and apply this understanding to specific circuits and to investigate neural disorders.
Our NSERC supported research is directed towards understanding the cellular and biochemical basis for activity-dependent and neuromodulator mediated enhancement of neurotransmitter release. Using microfluorometric imaging of fluorescent calcium indicators (fura-2, Ca2+-Green, Fura-Red, Fluo-4 etc.) we study the role of calcium and calcium-dependent processes in presynaptic terminals in modifying the probability of transmitter release in response to action potential activity. Much of this work was conducted in past years using crayfish neuromuscular synapses.
We have expanded our work on presynaptic terminals to look at Ca2+ influx in response to action potentials into accessory olfactory bulb mitral cell presynaptic terminals where they form synapses in the amygdala using transport of dextran conjugated Ca2+ indicators. Wanna look?. Presynaptic modulation by various neurotransmitters and the identification of calcium channel subtypes associated with transmitter release and facilitation was studied using this preparation by Sean Mulligan, who has recently joined the faculty of the Dept. of Physiology at the Univ. of Saskatchewan. After leaving my lab Sean did his PhD with Brian MacVicar while Brian was at Univ. of Calgary. Luckily, after many years in exile in the godforsaken frozen Albertan tundra Brian was lured to Vancouver by the siren song of the ever-perky servers on Granville Island: "Sir, I'll bring you that low fat latte out on the deck in just a moment, if you don't mind sitting in the sunshine while listening to the seagulls fight over your biscotti crumbs ".
Biophysical modeling studies have examined the consequences of molecular level colocalization of channels and vesicles in presynaptic active zones for Ca2+ diffusion and transmitter release was undertaken by Vahid Shahrezaei using numerical and Monte-Carlo simulations. This work is published: Vesicle PDF1 , Vesicle PDF2 and . Further modeling and experimental work on the effect of reducing the calcium channel density for calcium channel cooperativity at frog neuromuscular junction using w-conotoxin to block channels Vesicle PDF3 .
CIHR supported research includes projects integrating synaptic physiology and intrinsic electrophysiological properties of neurons into a network level framework to understand the temporal spatial dynamics that underlie neural processing of sensory signals by the olfactory bulb. For some of this work we have developed a novel in vitro nose-brain preparation that allows brain slice type experiments to be performed in a system where normal patterns of afferent input can be activated by application of odours to the nose. The work involves high speed imaging of Ca2+ and voltage sensitive dye signals from dendrites and/or nerve terminals brain of frogs during stimulation of olfactory epithelia with odours. Complimentary electrophysiological studies are used to relate the activity of individual neurons in the central nervous system (mitral cells and granule cells) to globally distributed oscillatory activity in networks of millions of cells during odour-induced activity. Recordings from mitral and granule cells during odour stimulation of the nose using the in vitro preparation are a significant part of this work. See Delaney and Hall, 1996 and Hall and Delaney, 2002, Davison et al., 2004 for further details. Ben Hall is now at Novartis in Zurich. Ian DAvison is on faculty at Boston University. Dr. Tibor Zelles of the Hungarian Academy, Institute for Experimental Medicine in Budapest undertook studies on the active properties of dendrites of granule cells using 2 photon imaging.
We have developed methods for selective filling of mitral cell apical dendritic tufts in glomeruli with Ca-Green that allow us to study the function of this superficial dendritic compartment in response to odour stimuli (Delaney et al., 2001). The pharmacology of the odour and shock-evoked Ca2+ transients is under investigation as well as the role of feedback inhibition in controlling the odour-evoked epsp at the distal dendritic input site. Ian Davison completed studies on dopaminergic modulation of transmitter release from mitral cell secondary dendrites using a combination of electrophysiology (whole cell recordings) and 2-photon imaging. See Delaney et al., 2001.
Dr. Jamie Johnston was supported by CIHR to study biophysical properties and dendritic distribution of low-voltage activated, T-type calcium channels in mouse mitral cells using a combination of whole cell electrophysiology and 2-photon calcium imaging. As of 2016 he is now a member of the research faculty at Univ. of Sussex. Dr. Adam Fekete joined the laboratory from Budapest in Jan. 2010 to continue eletrophysiological studies of olfactory bulb function and focused on the role of T-channels in supporting transmitter release from mitral dendrites. He is currently at the Univ. of Toronto (as of Summer 2014) with Lu-Yang Wang
Rett Syndrome research: During the past 8 years we have been working Rett syndrome research using a loss of function mouse model with a mutated non-functional Mecp2 gene (Jaenisch mouse). MeCP2 protein normally binds to methylated DNA acting as a transcription repressor to control many genes required for normal development. Loss of function in this gene is the cause of Rett Syndrome a neurodevelopmental disorder leading to severe cognitive and other systemic dysfunctions primarily in female children. We have crossed these mice with mice that express YFP in subsets of cortical neurons (Feng et al., 2000) to facilitate analysis of neuronal morphologies associated with the Rett phenotype and as a tool to evaluate the success (or failure) of therapeutic interventions. Current work funded by the International Rett Syndrome Foundation is investigating cell autonomous versus non-autonomous effects of this X-linked mutation on synaptic development and spinogenesis using immunohistochemistry Rietveld et al., 2015 and a transgenic mouse that expresses an MeCP2-GFP fusion protein that allows us to identify wild-type versus mutant neurons in mosaic female brains. More recent work (2019) has examined nicotinic cholinergic sensitivity of mutant versus wild-type neurons in brain slices completed by Azam Asgarihafshejani published in the journal Neuroscience.