Our laboratory studies the role of cardiac
related vagal afferents in the control hormone
release from the hypothalamus. These studies are
funded by NIH. We are currently working on a
project funded by Cyberonics Inc. to investigate
the effects of chronic vagal nerve stimulation
in unanaesthetized rats. In these studies, the
subjects are equipped with radio telemetry
transmitters to allow us to continuously record
blood pressure, heart rate, respiratory rate,
and general activity. We also perform
immunohistochemistry assays on the central
nervous system to identify brain areas that are
acutely and chronically activated by vagus nerve
stimulation. The vagus nerve stimulation
protocol that we use was determined by previous
studies funded by Cyberonics and was designed to
match the protocols being used clinically for
treatment resistant depression. Our preliminary
results show that acute (2 hour) and chronic (3
weeks) stimulation of the vagus nerve with these
parameters does not significantly affect blood
pressure, heart rate, respiratory rate, or
activity. The results of the
immunohistochemistry studies have shown that
several regions of the brain are activated by
vagal nerve stimulation. Among these regions are
brain areas that have been identified as
important in mood and cognitive function. These
results will be presented in a poster at the
Society for Neuroscience Meeting at Atlanta this
October. Continued availability of vagus nerve
stimulation for treatment resistant depression
will allow us to continue this research which
could lead to improvements in the use of vagus
nerve stimulation for treatment resistant
depression. This research may also lead to new
scientific discoveries resulting in better
treatment modalities for depression and other
debilitating neurological and psychiatric
illnesses.