RhoA regulates morphine associated NMDA receptor signaling in the prelimbic region of medial prefrontal cortex pyramidal neurons

Aims: Opioid dependence (OD) involves maladaptive neuroplasticity in brain reward circuits, particularly within the medial prefrontal cortex (mPFC). While the RhoA small GTPase and NMDA receptors (NMDARs) are both implicated in synaptic plasticity underlying addiction, their specific interaction within mPFC subregions and contribution to opioid induced neuroadaptations remain unclear.Methods: To evaluate the role of RhoA signaling in the prelimbic cortex (PLC), we assessed conditioned place preference (CPP) and locomotor sensitization following intra-PLC infusion of the RhoA inhibitor (Rhosin). We then employed western blotting, immunostaining, and in vitro electrophysiology in PLC slices to examine RhoA expression and its regulation of both synaptic and extrasynaptic NMDAR activity.Results: We found that intra-PLC inhibition of RhoA with Rhosin significantly attenuated morphine-induced CPP and locomotor sensitization. And repeated morphine administration upregulated RhoA expression in layer 5 pyramidal neurons of the PLC. Electrophysiologically, Rhosin application reduced the amplitude of NMDAR-mediated excitatory postsynaptic currents (EPSCs). By isolating extrasynaptic NMDAR currents using an activity-dependent MK-801 block, we demonstrated that RhoA inhibition also significantly reduced extrasynaptic NMDAR activation, likely by limiting glutamate spillover during high-frequency stimulation.Conclusion: RhoA signaling in the PLC mediates morphine induced neuroadaptations by regulating synaptic and extrasynaptic NMDAR activity, identifying it as a promising therapeutic target for opioid dependence.