Page 130 - NNS 2014 Program & Abstract Book

1Department of Child Health, University of Arizona College of
Medicine - Phoenix, Phoenix, USA
2BARROW Neurological Institute at Phoenix Children’s Hospital,
Phoenix, USA
3Phoenix VA Healthcare System, Phoenix, USA
Synaptogenesis is fundamental to the study of neuronal circuit reor-
ganization after diffuse traumatic brain injury (TBI), which depends
on astrocyte-secreted thrombospondins (TSP), glypicans (Gpc), and
hevin. These molecules have not been assessed in the context of TBI.
By investigating synaptogenic expression over time post-injury, we
can delineate synaptogenic events responsible for circuit reorganiza-
tion and their contribution to functional and behavioral change. We
hypothesize that TBI will change expression of astrocyte-secreted
synaptogenic molecules over a time course that may influence circuit
reorganization in the ventral posteromedial (VPM) thalamic nucleus.
In these experiments, male Sprague-Dawley rats (330–350 g) under-
went sham or moderate midline fluid percussion brain injury (mFPI;
1.9 atm; 6–10 min righting reflex). At multiple times points over 8
weeks post-injury, gene expression and protein levels of astrocyte-
secreted mediators of synaptogenesis were quantified from VPM tis-
sue biopsies. TSP1 gene expression was increased significantly at 1 d
and 5 d post-TBI in comparison to sham (p < 0.05). a2 d1, the receptor
for TSP, exhibited a significant decrease in gene expression at 3 d and
9 d post-injury compared to sham (p < 0.05). Gpc4 exhibited a sig-
nificant decrease at 7 d, 14 d, and 28 d compared to 1d post-TBI
(p < 0.05). Hevin exhibited a sustained injury-dependent decrease in
gene expression from 2 d-7 d post-TBI compared to sham (p < 0.05).
Corresponding protein level quantification is ongoing. Here we de-
termined a temporal profile of astrocyte-secreted synaptogenic gene
expression in the VPM after diffuse TBI that implicates astrocyte-
secreted molecules in circuit reorganization. Increased gene ex-
pression for TSP1 in the first week post-injury, in synchrony with
prolonged decreased expression of other astrocyte-secreted mediators
of synaptogenesis, supports a role for TSP1 as a primary mediator
of synaptogenesis after diffuse TBI. Prolonged decreased expression
of synaptogenic molecules after TBI implicates that mechanical for-
ces initiate a disease process, rather than an event.
Supported, in part by NIH R03 NS077098, NIH R01 NS065052,
and PCH Mission Support
Key words
astrocyte, circuit reorganization, diffuse brain injury, thrombospondin
C3-26
MORPHOLOGICAL REORGANIZATION OF THALAMIC
NEURONS AFTER DIFFUSE TBI MAY UNDERLIE ATTE-
NUATED IMMEDIATE EARLY GENE ACTIVATION
Rumney, B.M.1,2, Khodadad, A.2,5, Adelson, P.D.2,3, Lifshitz, J.2–4,
Thomas, T.C.2–4
1Biology and Biochemistry, University of Bath, Bath, UK
2Child Health, University of Arizona, College of Medicine, Phoenix,
USA
3BARROW Neurological Institute, Phoenix Children’s Hospital,
Phoenix, USA
4Phoenix VA Healthcare System, Phoeinx, USA
5Neuroscience, University of Strasbourg, Strasbourg, France
Diffuse traumatic brain injury (dTBI) causes late-onset, chronic sen-
sory sensitivity to whisker stimulation by 28 days post-injury (DPI)
after moderate midline fluid percussion injury (FPI). We hypothesize
that late-onset sensory sensitivity results from maladaptive circuit
reorganization within the thalamic relay of the whisker-barrel circuit
associated with changes in neuron morphology detected by impaired
circuit activation. Adult male, Sprague Dawley rats underwent
moderate midline FPI (1.9 atm, 6–10 min righting reflex) or sham
control procedures. Neuron morphology was quantified in the so-
matosensory thalamus at 1, 7, 28 and 56 DPI (n = 4/time point) in
Golgi stained tissue using MicroBrightField Neurolucida software.
Circuit activation at 28 DPI was evaluated by immediate early gene
(IEG) expression of ARC and EGR3 in the thalamus following
whisker stimulation at several time points (n = 4-5) using qPCR.
Golgi-stained neuron morphology revealed a significant decrease in
the number of branch points, ends and mean process length at 7DPI
in comparison to sham (p < 0.05). At 28 DPI, these parameters were
similar to sham. Sholl analysis indicated the greatest changes be-
tween 30–70lm from the soma. Whisker stimulation-induced IEG
ARC expression was significantly decreased in injured animals at 15
and 30 minutes post-stimulation compared to sham (p < 0.05). There
was no whisker stimulation or injury effect on EGR3 gene expres-
sion. Thus, thalamic neurons were truncated early, but returned to-
wards uninjured sham shape by 28 DPI; a time course paralleling
sensory sensitivity after diffuse TBI. Attenuated circuit activation
(ARC) at 28 DPI supported structural reorganization underlying
impaired circuit function in the latter phases of TBI. These outcome
measures may be critical in evaluating therapeutic approaches to
circuit restructuring.
Funding: NIH R03-NS077098, NIH R01-NS065052, Phoenix
Children’s Hospital Mission Support
Key words
circuit reorganization
C3-27
STIMULATION OF THE MEDIAL SEPTUM DRIVES HIP-
POCAMPAL THETA OSCILLATIONS LEADING TO PER-
SISTENT INCREASES IN THETA PHASE COHERENCE
Seidl, S.E., Izadi, A., Lee, D.J., Melnik, M., Ekstrom, A.D., Shahlaie,
K., Gurkoff, G.G.
University of California, Davis, Department of Neurological Surgery,
Davis, USA
Traumatic Brain Injury (TBI) attenuates hippocampal theta oscilla-
tions and is associated with poor episodic memory retrieval in rodents.
Previously, we demonstrated that 7.7 Hz theta stimulation of the
medial septal nucleus (MSN) for 1 minute prior to training in the
Barnes Maze task improved spatial learning in TBI injured rats. We
now hypothesize that minimizing the duration of stimulation to en-
train oscillations will allow for more physiological oscillatory patterns
and ultimately improve cognitive function. Sprague-Dawley rats
(300–350 g) underwent a lateral fluid percussion TBI (2.12-2.15 atm),
and were immediately implanted with three twisted bipolar electrodes:
MSN, ipsilateral hippocampus and ipsilateral medial pre-frontal cor-
tex (mPFC). Animals were tested four times on an object exploration
behavioral task and were randomly assigned to receive each of 0, 15,
30, or 60 seconds of pre-stimulation over these four trials. Theta
oscillation analysis included examining the percentage of time spent
oscillating in theta at each electrode and also the phase coherence of
theta between electrodes. Oscillations were evaluated 1 minute prior
to stimulation, during stimulation, and for 15 minutes during the be-
havioral task. During stimulation, coherence between mPFC-
hippocampus increased in a time-of-stimulation-dependent manner.
Stimulation also improved the percentage of time spent oscillating in
theta in both the mPFC and hippocampus. In addition, following 30 or
A-98