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I'm Stephane Oliet from Neurocentre
Magendie in Bordeaux, France
and I'm going to tell you about
the neuronal-glial
anatomical plasticity
that takes place in
the hypothalamus.
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The plasticity I'm
talking about takes
place in the
hypothalamo-neurohypophysial system.
The system is illustrated
in this diagram which
represents a sagittal view of
the basal part of the brain.
The hypothalamo-neurohypophysial
system is
made of neuroendocrine neurons,
shown here in yellow, and
that are localized in
both the supraoptic and
paraventricular nuclei.
The nuclei's perimeter here
is illustrated in green.
The magnocellular
neurons project
their axon directly into
the neurohypophysis
where they can release
in the bloodstream their
products of secretion,
namely oxytocin,
and vasopressin.
While oxytocin is important
for reproductive function,
alteration, and lactation,
vasopressin is essential for
cardiovascular and body
fluid homeostasis.
The release of these hormones in
the bloodstream is directly
dependent upon the
electrical activity
of the magnocellular
neuron activity,
which is itself controlled by
apparent excitatory and
arbitrary synaptic input.
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There are some specific
physiological conditions that are
associated with a
strong stimulation
of the magnocellular system,
such as chronic dehydration,
lactation, parturition,
or stress.
The hypothalamo-neurohypophysial
system undergoes
striking anatomical remodeling.
This remodeling is
characterized in
particular by hypertrophy
of the neuron
proportional increase
in the number of
the synopsis both
excitatory and inhibitory;
and most interestingly, a pronounced
reduction in the astrocytic coverage of
magnocellular neurons that
results in an increased amount of
directly juxtaposed
neuronal surfaces.
All of these changes
are completely
irreversible upon the
cessation of the stimulation.
