Manganaro and her colleagues focused on a two-hit pattern seen in stress research: an initial stressful event doesn’t cause lasting problems alone, but it quietly primes the brain, so a second, milder stressor later triggers far greater distress than it normally would. In mice, this showed up as social avoidance after two rounds of simulated social conflict a week apart.

The team tested whether drugs given before the first stressful encounter could block that priming and protect against future trauma-related sensitivity. Propranolol, a beta-blocker long used to treat high blood pressure and anxiety, worked. Mice given a single dose of propranolol still reacted normally to the first stressful event, but were shielded from the heightened sensitivity that usually followed the second. Manganaro’s team suggests the drug may interfere with how the brain consolidates traumatic memories, lowering the risk of PTSD-like symptoms taking hold after trauma.

Corticosterone, the rodent equivalent of the stress hormone cortisol, told a different story. Because PTSD is linked to low cortisol levels causing an increase of fear signals, giving a dose of the hormone shortly after trauma has been explored as a way to prevent the disorder. But in this study, acute administration of corticosterone failed to protect the mice, and higher doses even appeared to make them more vulnerable to the second stressor.

Together, the findings position propranolol as a promising candidate for stopping PTSD from taking root after trauma, while raising doubts about corticosterone-based prevention strategies. If the same window holds true in humans, the hours around a traumatic event may offer a rare chance to change its lasting impact.