Delayed loss of neurons occurs in mice with mild TBI and anxiety

Almeida-Suhett et al saw delayed loss of GABAergic interneurons in the BLA within the first week after mild CCI. (Representative photomicrographs of GAD-67 immunohistochemically stained GABAergic interneurons in the BLA of sham (left), 1-day CCI (middle), and 7-day CCI (right) animals. Total magnification is 630x; scale bar, 50 µm.)

Almeida-Suhett et al saw delayed loss of GABAergic interneurons in the BLA within the first week after mild CCI. (Representative photomicrographs of GAD-67 immunohistochemically stained GABAergic interneurons in the BLA of sham (left), 1-day CCI (middle), and 7-day CCI (right) animals. Total magnification is 630x; scale bar, 50 µm.)

Soldiers, athletes, and other individuals who suffer a traumatic brain injury often develop anxiety disorders, but scientists aren’t sure why. Some speculate that fear about future health or the stress of the trauma itself contributes to elevated anxiety, while others suspect changes happening inside the brain as a result of the injury are to blame.

Researchers at Maria Braga’s lab at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, recently found direct evidence that physical changes happen in the brain after TBI that coincide with increased anxiety levels.

She and her team studied a rat model of mild TBI, focusing on the basolateral amygdala (BLA) – a brain region often damaged by TBI, which has also been associated with increased fear and anxiety in instances of hyperactivity.

To find out what happens in the BLA that might be causing anxiety after a mild TBI, the researchers analyzed changes in synaptic activity in this region. Using Stereo Investigator with the optical fractionator probe to perform a stereological quantification of Nissl-stained and GAD-67 immunostained brain cells, they found that many of the inhibitory neurons – the cells that quiet activity – were lost seven days after injury. Whole cell recordings from principal neurons confirmed that the inhibitory cells’ synaptic transmissions were impaired during this period, resulting in increased excitability and “open field tests” showed elevated anxiety levels in post-injury rats at the exact same time point. Continue reading “Delayed loss of neurons occurs in mice with mild TBI and anxiety” »