Jenna Butterworth

Topic

Exploring the effects of ischemic stroke and diaschisis on connectomic presynaptic dendritic spine networks

Division of Medical Sciences

Date & location

• Thursday, September 12, 2024
• 12:30 P.M.
• Medical Sciences Building, Room 310

Examining Committee

Supervisory Committee

• Dr. Craig Brown, Division of Medical Sciences, University of Victoria (Supervisor)
• Dr. Leigh Anne Swayne, Division of Medical Sciences, UVic (Member)
• Dr. Brian Christie, Division of Medical Sciences, UVic (Member)

External Examiner

• Dr. John Taylor, Department of Biology, UVic

Chair of Oral Examination

• Dr. Theone Paterson, Department of Psychology, UVic

Abstract

Ischemic stroke is a life-threatening medical condition that can lead to dysfunction in brain regions both proximally and distally connected to the stroke site, a phenomenon known as “diaschisis”. Diaschisis can play an important role in recovery after stroke; however, the structural changes that occur at the level of neurons connected to the stroke site are not fully understood. Here, we performed confocal microscopy to visualize dendritic spines after a photothrombotic stroke in the primary somatosensory forelimb cortex (S1FL) of adult mice labeled with a retrograde adeno-associated virus (retro pAAV.CAG.GFP). This allowed for the visualization of presynaptic neurons directly connected to the infarct core. We observed a decrease in presynaptic spine density one week after stroke in superficial basilar dendrites within the peri-infarct region, which recovered by six weeks after stroke. An increase in dendritic spine density was also found six weeks after stroke within superficial primary apical dendrites in peri-infarct region, and within S2 in superficial primary and secondary apical dendrites as well as deep basilar dendrites. These results suggest that a retrograde degenerative signal may be localized to the peri-infarct region, whereas other factors may be playing a role in the widespread functional changes seen after stroke. The increase in dendritic spines seen in the peri-infarct and S2 regions six weeks after stroke may be playing an adaptive or compensatory role and aiding in recovery. Using a diaschisis model, these findings add novel information about neuronal structure proximal and distal to the infarct core, as well as elucidate potential degenerative and protective structural processes that may underly recovery after stroke.