Ketamine sex- and dose-dependently mitigates behavioral sequelae induced by a predator-based psychosocial stress model of post-traumatic stress disorder.

Current pharmacotherapy for post-traumatic stress disorder (PTSD), a debilitating psychiatric condition that develops in a subset of traumatized individuals, is inadequate. Over the past two decades, numerous studies have shown that ketamine, a non-competitive NMDA receptor antagonist, exerts rapid antidepressant effects in both humans and rodents, but the anxiolytic profile of ketamine, as well as its ability to treat PTSD-related symptoms, is still unclear. Thus, we examined the ability of a single administration of ketamine to prevent the onset of PTSD-like sequelae in a chronic psychosocial stress model of PTSD. Adult male and female Sprague-Dawley rats were exposed to a cat on two occasions, in combination with chronic social instability. Immediately following the cat exposure on Day 1, rats were given intraperitoneal injections of 10 mg/kg or 15 mg/kg ketamine or vehicle; control rats were injected with vehicle. Three weeks after the second cat exposure, we assessed symptoms of hyperarousal and anxiety-like behavior in the rats. In males, chronic stress led to greater anxiety on the elevated plus maze and in the open field; in females, chronic stress resulted in an exaggerated startle response and greater anxiety in the open field. These effects were most effectively prevented by the administration of 10 mg/kg ketamine. These findings demonstrate that ketamine can prophylactically prevent the onset of PTSD-like behaviors in males and females. Their sex-dependent nature is consistent with previous preclinical research and highlights the need for future research to examine their neurobiological basis.