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Molecular Basis of Compensatory Recovery in the CNS after Injury
HW Horch, L Saidenberg, M Chong, H Wadman, E Quenzer, M Friedlander, M Amano, P
Dickinson, A Pfister, O Ellers A Johnson
Biology and Neuroscience Departments
Bowdoin College
Background and Objectives: The consequences of injury in adult central nervous systems
(CNS) are often devastating and irreversible. In the cricket (Gryllus bimaculatus), unilateral
deafferentation of the auditory neurons of the prothoracic ganglia induces these cells to send
dendrites across the midline, a boundary they typically respect, to form functional synapses with
contralateral auditory afferents. This morphological compensatory growth is remarkably
precise, and has been shown to rapidly reinstate interneuron-specific tuning curves. Our goal is
to explore this phenomenon at the molecular, anatomical, and functional level.
Methods: Molecular changes were assessed using Q-PCR. Anatomical changes were
quantified using fluorescent neuronal tracers and confocal microscopy. Neurophysiological
recordings and negative phonotaxis analyses were used to assess functional recovery.
Results: Careful anatomical analyses indicate that deafferented dendrites sprout across the
midline and branch in a sexually dimorphic way. Semaphorins 1 and 2a showed no sexual
dimorphism, however, they are sequentially downregulated in correlation with dendritic midline
crossing and branching. The results of neurophysiological and behavioral assays are consistent
with functional recovery at the synaptic level.
Discussion and Conclusions: Our findings indicate that changes in the expression levels of
semaphorins after injury correlate with the deafferentation-induced plasticity seen in the auditory
system of the cricket, and that this plasticity has functional consequences for behavior.
Research reported in this project was supported by an Institutional Development Award (IDeA)
from the National Institute of General Medical Sciences of the National Institutes of Health under
grant number P20GM103423.