In addition to a severity spectrum that spans mild to severe, brain injuries may differ in terms of how male and female animals respond to them, according to Ramesh Raghupathi, a neurobiologist at Drexel University. Raghupathi and his colleagues have found that young male mice suffer more depressive behaviors than female mice at both four and eight weeks after mild TBI, and females display more headache-like symptoms after similar insults, which can include concussion. “All of these animals at these times after injury are cognitively normal,” Raghupathi told reporters. “And they do not have any movement problems.” Raghupathi and his colleagues also found molecular differences that may underlie the sex differences in TBI response that they observed. “In the male mice,” he said, “there is a dramatic difference in dopamine transmission” compared to the uninjured mice.” Researchers have previously linked impaired dopamine signaling to depression.
Raghupathi’s team tested for the lingering effects of TBI in mice by subjecting the animals to certain swimming tests—which are accepted as proxies for depression—and by using a thin filament to touch the faces of the rodents and recording their sensitivity as a measure of headache-like behaviors. Raghupathi said that he and his colleagues will now seek to further explore the molecular differences that may be at play behind the behavioral differences in male and female mice following TBI. “Our future work is developing these models and looking at the effect of dopaminergic signaling as the underlying basis of these problems,” he said.