Type 1 Corticotropin-Releasing Factor Receptor Differentially Modulates Neurotransmitter Levels in the Nucleus Accumbens of Juvenile versus Adult Rats

CRF regulates pain sensation by enhancement of corticoaccumbal excitatory synaptic transmission

Both peripheral and central corticotropin-releasing factor (CRF) systems have been implicated in regulating pain sensation. However, compared with the peripheral, the mechanisms underlying central CRF system in pain modulation have not yet been elucidated, especially at the neural circuit level. The corticoaccumbal circuit, a structure rich in CRF receptors and CRF-positive neurons, plays an important role in behavioral responses to stressors including nociceptive stimuli. The present study was designed to investigate whether and how CRF signaling in this circuit regulated pain sensation under physiological and pathological pain conditions. Our studies employed the viral tracing and circuit-, and cell-specific electrophysiological methods to label the CRF-containing circuit from the medial prefrontal cortex to the nucleus accumbens shell (mPFCCRF-NAcS) and record its neuronal propriety. Combining optogenetic and chemogenetic manipulation, neuropharmacological methods, and behavioral tests, we were able to precisely manipulate this circuit and depict its role in regulation of pain sensation. The current study found that the CRF signaling in the NAc shell (NAcS), but not NAc core, was necessary and sufficient for the regulation of pain sensation under physiological and pathological pain conditions. This process was involved in the CRF-mediated enhancement of excitatory synaptic transmission in the NAcS. Furthermore, we demonstrated that the mPFCCRF neurons monosynaptically connected with the NAcS neurons. Chronic pain increased the protein level of CRF in NAcS, and then maintained the persistent NAcS neuronal hyperactivity through enhancement of this monosynaptic excitatory connection, and thus sustained chronic pain behavior. These findings reveal a novel cell- and circuit-based mechanistic link between chronic pain and the mPFCCRF → NAcS circuit and provide a potential new therapeutic target for chronic pain.

MicroRNA-451a is a candidate biomarker and therapeutic target for major depressive disorder

Background

Increasing evidence supports the role of microRNAs (miRNAs) in major depressive disorder (MDD), but the pathophysiological mechanism remains elusive.

Aims

To explore the mechanism of microRNA-451a (miR-451a) in the pathology and behaviours of depression.

Methods

Abnormal miRNAs such as miR-451a reported previously in the serum of patients with MDD were screened and then confirmed in a mouse model of depression induced by chronic restraint stress (CRS). Eight-week-old male C57BL/6 mice had miR-451a overexpression in the medial prefrontal cortex (mPFC) via adeno-associated virus serotype 9 vectors encoding a pri-mmu-miR-451a-GFP fusion protein followed by behavioural and pathological analyses. Finally, molecular biological experiments were conducted to investigate the potential mechanism of miR-451a against depression.

Results

The serum levels of miRNA-451a were significantly lower in patients with MDD, with a negative correlation with the Hamilton Depression Scale scores. Additionally, a negative association between serum miR-451a and behavioural despair or anhedonia was observed in CRS mice. Notably, miR-451a expression was significantly downregulated in the mPFC of CRS-susceptible mice. Overexpressing miR-451a in the mPFC reversed the loss of dendritic spines and the depression-like phenotype of CRS mice. Mechanistically, miR-451a could inhibit CRS-induced corticotropin-releasing factor receptor 1 expression via targeting transcription factor 2, subsequently protecting dendritic spine plasticity.

Conclusions

Together, these results highlighted miR-451a as a candidate biomarker and therapeutic target for MDD.