The Distribution of Cytoplasmic and Membrane-Associated Tropomyosin-Related Kinase B (TrkB) Receptor in the Dendritic Tree of Adult Spinal Motoneurons
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Authors
Babaei Bourojeni, Farin
Date
2014-01-14
Type
thesis
Language
eng
Keyword
Microscopy , TrkB , Motoneuron , Dendrite
Alternative Title
Abstract
Although neurotrophins are conventionally associated with the proper growth and
survival of developing neurons, there is increasing evidence that they play an equally
significant role in the functions of adult neurons. Specifically, brain derived neurotrophic
factor activation of its preferred receptor TrkB is essential in the regulation of
motoneuronal activity. Neurotrophin‐dependent and independent activation of TrkB
regulates the motoneuronal dendritic integrity, and maintains unique classes of synapses. In
addition, it regulates the expression and function of ion channels as well as the strength of
inhibitory and excitatory synapses via different intracellular pathways. The recent
physiological findings in the regulatory roles of TrkB are implicative of its presence on
motoneuronal dendrites. Although, the expression of TrkB in the soma has long been
confirmed, its distribution on the dendritic tree of motoneurons remains unknown. We
aimed to examine the distribution of TrkB in the cytoplasm and membrane‐associated
regions of the dendritic tree of adult neck motoneurons.
We have determined, via confocal microscopy, that TrkB is present and abundant
throughout the cytoplasm and the membrane‐associated regions of motoneuronal dendrites
as well as the soma. TrkB is organized in clusters and its distribution is best described as
punctated. We then developed a technique to separately extract and quantify the TrkB
immunoreactivity associated with the membrane and the cytoplasm as function of distance
from the soma and dendritic tree. We have demonstrated that there is no bias in TrkB
immunoreactivity to a specific region of the dendritic tree in five trapezius motoneurons.
These observations were confirmed for both cytoplasmic and membrane‐associated TrkB.
There is compelling evidence that both mature full‐length and immature
hypoglycosylated TrkB isoforms are active in strengthening the response to excitatory
synapses in motoneurons. We identified the full length TrkB as well as 3 hypoglycosylated isoforms in cervical spinal segments that contain trapezius motoneurons and phrenic
motoneurons.
Taken together, these data indicate that TrkB is likely involved in regulating and
maintaining different classes of ion channels and synapses on the dendrites as well as the
soma. Various isoforms of TrkB may also be involved in regulating motoneuronal activity.
Description
Thesis (Master, Neuroscience Studies) -- Queen's University, 2014-01-14 12:48:21.357
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