The role of the galaninergic system in modulating stress-related responses in an animal model of posttraumatic stress disorder.

BACKGROUND

Converging evidence implicates the regulatory neuropeptide galanin in anxiety- and depression-related behaviors, through modulation of neuroendocrine, serotonergic, and noradrenergic systems. This study examined the relationship between stress-induced posttraumatic stress disorder (PTSD)-like behavioral response patterns in rats and galanin mRNA levels in key brain areas and the effects of acute phase pharmacologic manipulation using an agonist (galnon) on behavioral, physiologic, and response patterns of brain-derived neurotrophic factor (BDNF) and 5-hydroxytryptamine-1A (5HT-1A).

METHOD

Galanin mRNA expression was assessed in the frontal cortex and hippocampus in the short- and long-term (30 min and 7 days) after exposure to predator scent stress. The effects of intraperitoneal galnon .5 mg/kg versus saline 1 hour postexposure on behavioral tests (elevated plus maze and acoustic startle response) were evaluated 7 days later. Trauma-cue response, circulating corticosterone, and localized brain expression of 5HT-1A receptors and BDNF were subsequently assessed. All data were analyzed in relation to individual behavior patterns.

RESULTS

Whereas animals with minimal behavioral disruption displayed a lasting upregulation of galanin mRNA in the hippocampal CA1 area, those with extreme behavioral responses displayed downregulation in both CA1 and frontal cortex. Immediate postexposure treatment with galnon significantly reduced prevalence rates of extreme responders, reduced trauma-cue freezing responses, corrected the corticosterone response, and increased CA1 expression of 5HT-1A and BDNF mRNA compared with saline controls.

CONCLUSIONS

Galanin is actively involved in the neurobiological response to predator scent stress with resilience/recovery after stress exposure and thus warrants further study as a potential therapeutic avenue for the treatment of anxiety-related disorders.