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Michael Jonz - Research

I am a neurobiologist interested in the physiology, morphology, and development of sensory systems in vertebrates.  Research in my lab is currently focused on the cellular mechanisms of oxygen “sensing” in the gills of fish and amphibians by peripheral chemoreceptors, and the process of cardiorespiratory regulation.  In addition, my research program includes studies designed to investigate the role of ion channels in visual processing in the retina.  I primarily use the zebrafish (Danio rerio), goldfish (Carassius auratus) and larvae of the African clawed frog (Xenopus laevis) to address these issues.

Major Research Interests:

1. Cellular mechanisms of O2 chemoreception in the gill
Vertebrates respond to low O2 (hypoxia) with hyperventilation and other physiological changes.  Specialized O2 chemoreceptors “sense” chemical changes in blood or environmental O2 and initiate these adaptive responses via the nervous system.  In our lab, we use patch-clamp electrophysiological recording of isolated O2 chemoreceptors from the gills of fish and amphibian larvae to study the cellular processes by which these cells receive, and respond to, hypoxic stimuli.  Membrane ion channels, such as K+ channels, are sensitive to changes in O2 and play a major role in O2 sensing.

2. Morphology and neurochemistry of O2 sensing
The underlying neural pathways and neurotransmitters involved in O2 sensing in aquatic vertebrates are unknown.  Using high-resolution microscopy, combined with immunohistochemical techniques, we characterize the innervation patterns of O2 chemoreceptors at various stages of development.  In addition, we perform in vivo screening of exogenously applied neurochemicals to identify the neurotransmitters and receptors involved.

3. Development of O2-sensing pathways
The formation of O2-sensing pathways is not clear in any organism.  Using electrophysiological and confocal techniques, we study the appearance and innervation of O2 chemoreceptors during early developmental stages in zebrafish embryos and early-stage larvae.

4. Visual processing and feedback in the outer retina
In the central nervous system (CNS), changes in pH can produce significant modulation of neuronal excitability, membrane potential and synaptic transmission.  Transient changes in extracellular pH occur in the retina and may have profound effects on visual processing due to the pH sensitivity of ion channels.  We perform patch-clamp recordings on isolated horizontal cell neurons of the vertebrate retina as a convenient model for studying ion channel modulation and potential roles in feedback.  These cells form synaptic connections with light-sensitive photoreceptors and play a major role in such visual processes as contrast enhancement and colour opponency.  We also study how retinal neurons of hypoxia-tolerant organisms (such as goldfish) deal with hypoxia, such as during an ischemic challenge.