Neuropeptide FF Receptor Activates the Stress Axis and Triggers Anxiety-Like Behavior in Rodents | Research

The takeaway

Activating the NPFFR2 neuropeptide receptor in the hypothalamus directly stimulates the HPA stress axis and produces anxiety-like behavior in mice, revealing a new neuropeptide pathway in stress and anxiety regulation.

First-ever demonstration
This is the first study showing that NPFFR2 activation directly stimulates the HPA stress axis and triggers anxiety-like behavior

What the researchers found

NPFFR2 agonists (dNPA administered ICV and AC-263093 administered IP) increased serum corticosteroid levels in a time-dependent manner (rats) and dose-dependent manner (mice). These effects were blocked by:

- RF9 (NPFF receptor antagonist, ICV)

- α-helical CRF(9-41) (CRF receptor antagonist, IV)

AC-263093 also increased c-Fos expression in the hypothalamic paraventricular nucleus (confirming neuronal activation in the HPA axis command center) and induced anxiogenic effects in mice on the elevated plus maze. This is the first demonstration that NPFFR2 directly activates the HPA axis and triggers anxiety-like behaviors.

Why it matters

The HPA stress axis is central to anxiety disorders, depression, and PTSD. Most research has focused on CRF as the primary driver of this axis. Discovering that NPFFR2 — a receptor for a completely different neuropeptide family — can independently activate the HPA axis opens a new therapeutic target. NPFFR2 antagonists could potentially reduce pathological stress responses without the issues associated with directly blocking the CRF system.

How the study worked

NPFFR2 agonists were administered to rats (ICV, intracerebroventricularly) and mice (IP, intraperitoneally). Serum corticosteroid levels were measured at multiple time points and doses. Receptor specificity was confirmed using the NPFF receptor antagonist RF9 and the CRF antagonist α-helical CRF(9-41). c-Fos immunohistochemistry assessed neuronal activation in the hypothalamic paraventricular nucleus. Anxiety-like behavior was evaluated using the elevated plus maze in mice.

What this study cannot tell us

This is a preclinical study in rodents — direct translation to human anxiety and stress disorders is uncertain. The pharmacological tools (agonists and antagonists) may not be perfectly selective for NPFFR2. The elevated plus maze measures anxiety-like behavior but does not directly assess the subjective experience of anxiety. The CRF antagonist blockade suggests NPFFR2 works upstream of CRF, but the precise neural circuit was not fully mapped.

How to read the evidence

This is a preclinical pharmacology study in rodents with strong mechanistic controls (dual antagonist blockade). The evidence clearly demonstrates the NPFFR2-HPA axis link in animals but has no human clinical data.

When this study was published

Published in 2017, this study established a foundational finding that has informed subsequent research on NPFF's role in stress and emotional regulation.

The bigger picture

The RFamide family of neuropeptides — which includes NPFF, kisspeptin, and RFRP (GnIH) — is increasingly recognized as important modulators of neuroendocrine function. This study adds stress and anxiety regulation to NPFF's portfolio, alongside its known roles in pain modulation and opioid tolerance. The convergence of NPFFR2 signaling onto the CRF/HPA pathway suggests complex neuropeptide crosstalk in the hypothalamus that may be relevant to multiple psychiatric and endocrine conditions.

Questions still open

Would NPFFR2 antagonists have anxiolytic effects in rodent models of pathological anxiety or chronic stress?
Is NPFFR2 expression or signaling altered in human anxiety disorders or post-traumatic stress disorder?
How does NPFFR2 interact with other hypothalamic neuropeptide systems (e.g., orexin, neuropeptide Y) in regulating stress responses?

Common questions

What is Neuropeptide FF and what does it normally do?

Neuropeptide FF (NPFF) is a member of the RFamide family of brain peptides. It was originally discovered as a 'morphine-modulating peptide' — it can reduce the pain-relieving effects of opioids. It works through two receptors (NPFFR1 and NPFFR2) and also helps regulate body temperature, feeding, and reproductive hormones. This study adds stress response and anxiety to its known functions.

Could blocking this receptor help treat anxiety?

Potentially. Since activating NPFFR2 causes anxiety-like behavior and stress hormone release, blocking it with an antagonist drug might have the opposite effect — reducing anxiety and dampening excessive stress responses. However, this has not yet been tested in anxiety disorder models, and the specific role of NPFFR2 in human anxiety remains to be established.

Read the original research

NPFFR2 Activates the HPA Axis and Induces Anxiogenic Effects in Rodents.

International journal of molecular sciences, 18(8)

View on PubMed ↗Publisher’s paper ↗

Citation

Lin, Ya-Tin; Yu, Yu-Lian; Hong, Wei-Chen; Yeh, Ting-Shiuan; Chen, Ting-Chun; Chen, Jin-Chung. (2017). NPFFR2 Activates the HPA Axis and Induces Anxiogenic Effects in Rodents.. International journal of molecular sciences, 18(8). https://doi.org/10.3390/ijms18081810