Cocaine memory reactivation induces functional adaptations within parvalbumin interneurons in the rat medial prefrontal cortex

Abstract

Substance use disorder is a complex disease created in part by maladaptive learning and memory mechanisms following repeated drug use. Exposure to drug‐associated stimuli engages prefrontal cortex circuits, and dysfunction of the medial prefrontal cortex (mPFC) is thought to underlie drug‐seeking behaviors. Growing evidence supports a role for parvalbumin containing fast‐spiking interneurons (FSI) in modulating prefrontal cortical microcircuit activity by influencing the balance of excitation and inhibition, which can influence learning and memory processes. Most parvalbumin FSIs within layer V of the prelimbic mPFC are surrounded by specialized extracellular matrix structures called perineuronal nets (PNN). Previous work by our group found that cocaine exposure altered PNN‐surrounded FSI function, and pharmacological removal of PNNs reduced cocaine‐seeking behavior. However, the role of FSIs and associated constituents (parvalbumin and PNNs) in cocaine‐related memories was not previously explored and is still unknown. Here, we found that reactivation of a cocaine conditioned place preference memory produced changes in cortical PNN‐surrounded parvalbumin FSIs, including decreased parvalbumin intensity, increased parvalbumin cell axis diameter, decreased intrinsic excitability, and increased excitatory synaptic input. Further investigation of intrinsic properties revealed changes in the interspike interval, membrane capacitance, and afterhyperpolarization recovery time. Changes in these specific properties suggest an increase in potassium‐mediated currents, which was validated with additional electrophysiological analysis. Collectively, our results indicate that cocaine memory reactivation induces functional adaptations in PNN‐surrounded parvalbumin neurons, which likely alters cortical output to promote cocaine‐seeking behavior.

Diurnal changes in perineuronal nets and parvalbumin neurons in the rat medial prefrontal cortex

“…analysis to identify single- [59], double-labeled [60], and triple-labeled [48] neurons. Labeling was quantified bilaterally in the prelimbic mPFC using Pipsqueak AI software.…”

“…Immunohistochemical methods were similar to those previously described [60][61][62][63]. Solutions were prepared in either 0.1 M phosphate buffer at pH 7.4 (PB) or 0.1 M Tris-buffered saline at pH 7.6 (TS).…”

“…Confocal imaging was performed as described previously [60,61]. Two high magnification images were taken at each rostral-caudal level of the prelimbic mPFC (2 images/level x 2 levels/animal = 4 images/animal).…”

“…Only one cell per rat was used for each experiment so that reported N-sizes represent the number of animals. Recording conditions and solutions for whole-cell recordings were as previously described [60,61]. Rats were briefly anesthetized with isoflurane and intracardially perfused with ice cold recovery solution: (in mM) Peak AMPAR excitatory postsynaptic current (EPSC) amplitudes were measured at 20-25 min in d-APV, and this EPSC was subtracted from 5 min averages of baseline EPSCs to obtain the peak NMDAR EPSC [65].…”

014 Diurnal changes in perineuronal nets and parvalbumin neurons in the rat medial prefrontal cortex

“…Pipsqueak AI identify individual PV+ cells, PNNs, 8-oxo-dG, or OTX2-labeled cells, which were then verified by a trained experimenter who was blinded to the experimental conditions. The plug-in compiles this analysis to identify single- (Slaker et al 2016b), double-labeled (Jorgensen et al 2020), and triple-labeled (Harkness et al 2019) neurons. Labeling was quantified bilaterally in the prelimbic mPFC using Pipsqueak AI software.…”