Brain-wide mapping of c-fos expression in the single prolonged stress model and the e ff ects of pretreatment with ACH-000029 or prazosin

Post-traumatic stress disorder (PTSD) is a mental health condition that is triggered by a stressful event, with symptoms including exaggerated startle response, intrusive traumatic memories and nightmares. The single prolonged stress (SPS) is a multimodal stress protocol that comprises a sequential exposure to physical restraint, forced swimming, predator scent and ether anesthesia. This procedure generates behavioral and neurobiological alterations that resemble clinical findings of PTSD, and thus it is commonly used to model the disease in rodents. Here, we applied c-fos mapping to produce a comprehensive view of stress-activated brain regions in mice exposed to SPS alone or to SPS after oral pretreatment with the serotonin-noradrenaline receptor dual modulator ACH-000029 or the alpha 1-adrenergic blocker prazosin. The SPS protocol evoked c-fos expression in several brain regions that control the stress-anxiety response, including the central and medial amygdala, the bed nucleus of the stria terminalis, the pallidum, the paraventricular hypothalamus, the intermediodorsal, paraventricular and central medial thalamic nuclei, the periaqueductal gray, the lateral habenula and the cuneiform nucleus. These effects were partially blocked by pretreatment with prazosin but completely prevented by ACH-000029. Collectively, these findings contribute to the brain-wide characterization of neural circuits involved in PTSDrelated stress responses. Furthermore, the identification of brain areas regulated by ACH-000029 and prazosin revealed regions in which SPS-induced activation may depend on the combined or isolated action of the noradrenergic and serotonergic systems. Finally, the dual regulation of serotonin and alpha 1 receptors by ACH-000029 might represent a potential pharmacotherapy that can be applied in the peri-trauma or early post-trauma period to mitigate the development of symptoms in PTSD patients.