COCAINE WITHDRAWAL REGULATES PREFRONTAL NEURONAL MATURATION AND DISRUPTS OUTCOME EVALUATION
Authors: Lu *Tangsheng , Li Xue , Liu Xiaoxing , Zheng Wei , Han Yin , Lu Lin 
Published: February 2025

Abstract

Background
Relapse typically occurs after a prolonged period of abstinence, often triggered by re- exposure to cues associated with prior cocaine use. Craving for cocaine exhibits a progressive increase during the initial weeks of withdrawal. This phenomenon is thought to be associated with potential alterations in the excitability and maturity of neurons within the prelimbic cortex (Prl)[1]. Decision- making related to drug seeking involves a process of self-evaluation based on physiological and psychological sensations. Research indicates that the Prl plays a crucial role in the assessment of outcome evaluation[2]. Our hypothesis posits that withdrawal induces changes in Prl neurons, which disrupt the outcome evaluation, ultimately leading to an increase in drug craving.

Aims & Objectives
1. Integrate operant behavior and fiber photometry 2. 3D Reconstruction and Identification of Dendritic Spines 3. Investigate prefrontal cortex CaMKII neuronal activity while rat is performing behavioral tasks.

Method
Rats underwent training to self-administer cocaine within operant conditioning chambers, where pressing the active lever resulted in the delivery of a cocaine infusion. The rats were subsequently tested on either day 2 or day 29 of abstinence, during which we recorded Prl CaMKII neuron responses by fiber photometry system. In addition, another set of experiments involved the 3D reconstruction and analysis of dendritic spines in Prl cortex CaMKII neurons. The rats were subjected to Water Delivery Task which fluids (water, sucrose, or quinine) were delivered intraorally through a cheek fistula. On either day 3, 4 or day 30, 31 of abstinence, during which we recorded Prl CaMKII neuron responses.

Results
After a 10-day self-administration training period, on day 29 of testing following cocaine withdrawal, rats exhibited a significant increase in craving as measured by active nose-poke when compared to day 2. Subsequently, we conducted a 3D reconstruction and analysis of dendritic spines in Prl CaMKII neurons. Our findings revealed that withdrawal resulted in morphological changes in these neurons. Furthermore, we recorded the responses of Prl CaMKII neurons during testing, revealing that after 29 days of withdrawal, these neurons exhibited a significantly increased responses to cues.
Subsequently, we conducted a Water Delivery Task, utilizing sucrose and quinine as stimuli, to assess the encoding of different (positive/negative) value stimuli of PrL neurons. Our results indicate that withdrawal reshapes the responses of these neurons to stimuli. Recent research findings suggest that Prl CaMKII neurons encode outcome evaluation. Our study implies that this neural population may be disrupted by cocaine withdrawal, thereby affecting outcome evaluation. In summary, our findings imply that withdrawal disrupts the morphology of Prl CaMKII neurons, consequently impairing their outcome evaluation function, which may serve as a crucial factor contributing to relapse.

Discussion & Conclusion
Current findings suggest that cocaine withdrawal disrupts the outcome evaluation function associated with rats' Prl CaMKII neurons. This mis-evaluation may lead to impairments of decision-making functions, ultimately contributing to relapse. However, we intend to provide more profound evidence in subsequent research to establish that Prl CaMKII neurons encode outcome evaluation.

References
[1] Liu X, Yuan K, Lu T, et al. Preventing incubation of drug craving to treat drug relapse: from bench to bedside. Mol Psychiatry. 2023;28(4):1415-1429. doi:10.1038/s41380-023-01942-2
[2] Rudebeck PH, Saunders RC, Prescott AT, Chau LS, Murray EA. Prefrontal mechanisms of behavioral flexibility, emotion regulation and value updating. Nat Neurosci. 2013;16(8):1140-1145. doi:10.1038/nn.3440