Milanes, S. | bioRxiv Science

bioRxiv2026

Arrestin-3 promotes locomotor sensitization to psychostimulants via JNK signaling in nucleus accumbens

Arrestins play key role in desensitization of G protein-coupled receptors. Direct signaling role of arrestins has also been documented. Two ubiquitously expressed arrestin isoforms, arrestin-2 and -3 (Arr3), perform similarly in receptor desensitization and share many signaling functions, enabling them to substitute for one another. However, certain signaling roles are specific to each isoform. Mice lacking Arr3 (A3KO) show blunted acute responsiveness to the locomotor stimulatory effect of amphetamine (AMPH). Here we demonstrate that AMPH- and cocaine-induced locomotion of A3KO mice is significantly reduced. This loss-of-function phenotype suggests that Arr3-mediated signaling contributes to the effect. Virus-driven expression of Arr3 in caudate-putamen of A3KO and wild type mice suppressed AMPH-induced locomotion. In contrast, restoration of Arr3 in nucleus accumbens rescued locomotor response. Thus, in caudate-putamen Arr3 participates in the desensitization of dopamine receptors, whereas Arr3-dependent signaling in nucleus accumbens underlies the molecular mechanism of the locomotor response and sensitization. Using monofunctional Arr3-derived peptides, we showed that in the nucleus accumbens Arr3 promoted drug-induced locomotor responses via facilitation of JNK3 activation.

neuroscience↗

bioRxiv2025

Preserved synaptic architecture but impaired ketamine-induced synaptic plasticity of layer 5 pyramidal neurons in the aged frontal cortex

Healthy aging is accompanied by a gradual decline in higher-order cognitive functions, including working memory, attention, and cognitive flexibility, processes that critically rely on intact frontal cortical circuits. While neuronal loss is minimal during aging, whether there are changes in functional plasticity in this region remains unexplored. In this regard, dendritic spines, the primary postsynaptic structures of excitatory synapses, act as key hubs for experience-dependent synaptic remodeling. Using longitudinal in vivo two-photon imaging in Thy1-eGFP-M mice, we examined age-related changes in dendritic spine density and dynamics in layer 5 pyramidal neurons of the secondary motor area (MOs), a frontal cortical region essential for strategy switching and cognitive flexibility, and that was assessed using an operant conditioning paradigm. We found that aged mice (18-22 months) exhibited significant impairments in cognitive flexibility relative to young mice (3-5 months) in the four-odor choice discrimination and reversal task. Analysis of dendritic spine plasticity revealed that baseline spine density, turnover, and morphology were largely preserved in aged mice. Sex differences were evident, with females displaying higher spine density and a greater fraction of stable spines, a feature maintained across aging. Importantly, despite preserved baseline architecture, aged mice showed impaired ketamine-induced spinogenesis and reduced stabilization of newly formed spines, in contrast to the robust structural plasticity observed in young mice. These results indicate that healthy aging selectively impairs activity-dependent synaptic remodeling without affecting steady-state spine architecture in frontal cortical circuits. By linking deficits in induced synaptic plasticity to age-related impairments in cognitive flexibility, our study highlights the critical need to target plasticity mechanisms as a therapeutic strategy to restore executive function and cognitive adaptability in the aging brain.

neuroscience↗