Acute and Protracted Abstinence from Methamphetamine Bidirectionally Changes Intrinsic Excitability of Indirect Pathway Spiny Projection Neurons in the Dorsomedial Striatum

Methamphetamine (meth) is an addictive psychostimulant and illicit use presents significant personal and socioeconomic harm. Behavioral studies support the involvement of the dorsal striatum in drug-seeking but stimulant induced dysfunction in this region is understudied. The dorsal striatum can be subdivided into the dorsomedial (DMS) and dorsolateral (DLS) striatum with the DMS implicated in goal-directed and DLS in habitual behaviors; both regions are primarily composed of GABAergic direct (dSPNs) and indirect pathway (iSPNs) spiny projection neurons. To examine the effect of repeated meth on SPNs, mice were administered meth (2 mg/kg) for ten consecutive days and intrinsic excitability, dendritic excitability, and spine density were examined. DMS iSPN intrinsic excitability was increased at 1 day but decreased at 21 days of abstinence. In contrast, DMS dSPN intrinsic excitability was unchanged at either timepoint. Dendritic excitability and spine densities were unaltered in DMS iSPNs and dSPNs at 1 and 21 days of abstinence. The effect of repeated meth on iSPN excitability was specific to the DMS; DLS iSPN intrinsic excitability, dendritic excitability, and spine density were unchanged at 1 and 21 days of abstinence. These findings point toward DMS iSPN dysfunction in meth use disorders with differential dysfunction dependent on abstinence duration.