A mouse study found that a brain peptide called cortistatin-14 (CST-14) quickly lifts depressive‑like behavior, and this effect depends on the ghrelin receptor and GABA‑A signaling. When the ghrelin receptor was blocked with the compound [D‑Lys3]GHRP‑6, the antidepressant effect disappeared, showing that GHRP‑6 acts as a ghrelin‑receptor antagonist in the brain. The work suggests that messing with ghrelin signaling can influence mood, but it doesn’t give a clear dosing or usage guide for people.

Cortistatin-14 (CST-14), a recently discovered cyclic neuropeptide, can bind to all five cloned somatostatin receptors (SSTRs) and ghrelin receptor to exert its biological activities and co-exists with GABA within the cortex and hippocampus. However, the role of CST-14 in the control of depression processes is not still clarified. Here, we tested the behavioral effects of CST-14 in the in a variety of classical rodent models of depression [forced swimming test (FST), tail suspension test (TST) and novelty-suppressed feeding test]. In the models of depression, CST-14 produced antidepressant-like effects, and does not altered locomotor activity levels. And, we found that CST-14 mRNA and BDNF mRNA were significantly decreased in the hippocampus and cortex after mice exposed to stress. Further data show that i.c.v. administration of CST-14 produce rapid antidepressant effects, and does not altered locomotor activity levels. Then these antidepressant-like effects were significantly reversed by [D-Lys₃]GHRP-6 (ghrelin receptor antagonist), but not c-SOM (SSTRs antagonist). Meanwhile, the effects of some neurotransmitter blockers indicates that only GABA_A system, but not CRF1 receptor, &#x3b1;/&#x3b2;-adrenergic receptor, is involved in the antidepressant effect of CST-14. The effects of the mTOR inhibitor (rapamycin), the PI3K inhibitor (LY294002) and the p-ERK1/2 inhibitor (U0126) suggesting that the ERK/mTOR or PI3K/Akt/mTOR signaling pathway is not involved in the antidepressant effects of CST-14. Interestingly, intranasal administration of CST-14 led to reducing depressive-like behavior, and near-infrared fluorescent experiments showed the real-time <i>in vivo</i> bio-distribution in brain after intranasal infusion of Cy7.5-CST-14. Taken all together, the results of present study point to a role for CST-14 in the modulation of depression processes via the ghrelin and GABA_A receptor, and suggest cortistation may represent a novel strategy for the treatment of depression disorders. <b>Highlights:</b> -CST-14 and BDNF mRNA are decreased in hippocampus and cortex once mice exposed to stress.-i.c.v. or intranasal administration of CST-14 produce rapid antidepressant effects.-NIR fluorescence imaging detected the brain uptake and distribution after intranasal CST-14.-Antidepressant effects of CST-14 were only related to ghrelin and GABA_A system.-Co-injection of CST-14 and NPS produce antidepressant effect, and do not impair memory.