NPY, a neuropeptide that is widely distributed in the brain, has anxiolytic-like effects in rodents and is thought to enhance cognition under stressful conditions. NPY also counteracts the anxiogenic effects of CRH in the amygdala, the hippocampus, the hypothalamus and the locus coeruleus, and resilience might involve maintaining a balance between NPY and CRH levels during stress33. In a study of special forces soldiers, who are considered to be highly stress resilient, higher NPY levels during rigorous military training were associated with better performance34. Another study found higher plasma NPY levels in combat-exposed veterans without PTSD than in those with PTSD35. These findings in humans are consistent with recent studies in rats: central administration of NPY in rats inhibits the development, and promotes the extinction, of fear conditioning, with NPY antagonists exerting the opposite actions. These effects are mediated at least in part by the amygdala36. Moreover, intra-amygdala NPY administration promotes resilient responses to stress, in the form of reduced anxiety-like behaviours in response to acute restraint37.
