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Aims: Central melanocortin 4 receptor (MC4R) has been reported to induce anhedonia via eliciting dysfunction of excitatory synapses. It is evident that metabolic signals are closely related to chronic stress‐induced depression. Here, we investigated that a neural circuit is involved in melanocortin signaling contributing to susceptibility to stress. Methods: Chronic social defeat stress (CSDS) was used to develop depressive‐like behavior. Electrophysiologic and chemogenetic approaches were performed to evaluate the role of paraventricular thalamus (PVT) glutamatergic to nucleus accumbens shell (NAcsh) circuit in stress susceptibility. Pharmacological and genetic manipulations were applied to investigate the molecular mechanisms of melanocortin signaling in the circuit. Results: CSDS increases the excitatory neurotransmission in NAcsh through MC4R signaling. The enhanced excitatory synaptic input in NAcsh is projected from PVT glutamatergic neurons. Moreover, chemogenetic manipulation of PVTGlu‐NAcsh projection mediates the susceptibility to stress, which is dependent on MC4R signaling. Overall, these results reveal that the strengthened excitatory neurotransmission in NAcsh originates from PVT glutamatergic neurons, facilitating the susceptibility to stress through melanocortin signaling. Conclusions: Our results make a strong case for harnessing a thalamic circuit to reorganize excitatory synaptic transmission in relieving stress susceptibility and provide insights gained on metabolic underpinnings of protection against stress‐induced depressive‐like behavior. [ABSTRACT FROM AUTHOR]

Summary: Aims: Palmitoylation of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptors (AMPARs) subunits or their "scaffold" proteins produce opposite effects on AMPAR surface delivery. Considering AMPARs have long been identified as suitable drug targets for central nervous system (CNS) disorders, targeting palmitoylation signaling to regulate AMPAR function emerges as a novel therapeutic strategy. However, until now, much less is known about the effect of palmitoylation‐deficient state on AMPAR function. Herein, we set out to determine the effect of global de‐palmitoylation on AMPAR surface expression and its function, using a special chemical tool, N‐(tert‐Butyl) hydroxylamine (NtBuHA). Methods: BS3 protein cross‐linking, Western blot, immunoprecipitation, patch clamp, and biotin switch assay. Results: Bath application of NtBuHA (1.0 mM) reduced global palmitoylated proteins in the hippocampus of mice. Although NtBuHA (1.0 mM) did not affect the expression of ionotropic glutamate receptor subunits, it preferentially decreased the surface expression of AMPARs, not N‐methyl‐d‐aspartate receptors (NMDARs). Notably, NtBuHA (1.0 mM) reduces AMPAR‐mediated excitatory postsynaptic currents (mEPSCs) in the hippocampus. This effect may be largely due to the de‐palmitoylation of postsynaptic density protein 95 (PSD95) and protein kinase A‐anchoring proteins, both of which stabilized AMPAR synaptic delivery. Furthermore, we found that changing PSD95 palmitoylation by NtBuHA altered the association of PSD95 with stargazin, which interacted directly with AMPARs, but not NMDARs. Conclusion: Our data suggest that the palmitoylation‐deficient state initiated by NtBuHA preferentially reduces AMPAR function, which may potentially be used for the treatment of CNS disorders, especially infantile neuronal ceroid lipofuscinosis (Batten disease). [ABSTRACT FROM AUTHOR]