[Abstract Title]. - Society for Neuroscience

intracerebroventricular (i.c.v.) cannula guide. At least one week later, Mn 2+ (500mM, i.c.v.) was
administered 1 h prior to a 15 min swim stress (n=10) in room temperature water (30 cm depth).
Control rats (n=10) were handled 1 h after Mn 2+ administration. Rats were transcardially
perfused with 4% paraformaldehyde and sacrificed 6 h, 24 h, 48 h, or 72 h after swim stress and
brains were removed. The brains were scanned with a 9.4 T vertical bore magnet and areas of
increased activity were analyzed using a program written in IDL virtual machine. The presence
of Mn 2+ was detected in brain in a time-dependent manner. Thus, at 6 h Mn 2+ was present
primarily in the ventricles and there was little difference between swim stress and control rats.
By 24 h and 48 h, Mn 2+ was visualized in specific brain nuclei, and fiber tracts became visible at
48 h. By 72 h there was little enhancement left. Swim stress increased Mn 2+ labeling at both 24 h
and 48 h in specific brain regions. Enhancements were observed in the bed nucleus of the stria
terminalis and the dorsal hippocampus, areas that mediate stress related behaviors and regulate
the hypothalamic-pituitary adrenal axis. Additionally, enhanced labeling was seen in the lateral
periaqueductal gray (lPAG), a brain region that has been proposed to mediate escape behaviors
and active coping strategies. This labeling is consistent with the escape behavior (climbing and
swimming) observed during initial exposure to swim stress. Through these experiments we have
found that MEMRI is a rapid way of identifying structures activated by stress in 3 dimensions.
These are the first studies, to our knowledge, to use MEMRI to examine brain circuitry activated
by an acute stressor. This technique has much promise for revealing the mechanisms by which
stress impacts on the brain and how this might be altered by pharmacological agents.
Disclosures: D.A. Bangasser , None; Y. Perez, None; B. Brockel, Full time employee of
AstraZeneca, A. Employment (full or part-time); Stock options for AstraZeneca, E. Ownership
Interest (stock, stock options, patent or other intellectual property); R.J. Valentino, None.
Poster
286. Imaging the Nervous System
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 286.3/QQ43
Topic: E.09.b. Blood flow
Support: NIH Grant NS-051188
NIH Grant EB00790
Title: In vivo two-photon measurement of single vessel diameter changes using astrocytic
indicator SR101