Chronic methamphetamine administration produces cognitive deficits through augmentation of GABAergic synaptic transmission in the prefrontal cortex

BACKGROUNDChronic methamphetamine (METH) abuse is associated with the emergence of cognitive deficits and hypofrontality, a pathophysiological marker of many neuropsychiatric disorders that is produced by altered balance of local excitatory and inhibitory synaptic transmission. However, there is a dearth of information regarding the cellular and synaptic mechanisms underlying METH-induced cognitive deficits and associated hypofrontal states. METHODSRats went through a METH sensitization regime or saline (SAL) consisting of 14 days of METH treatment (day 1 and 14, 1 mg/kg; days 2-13, 5 mg /kg) followed by 7-10 days of home cage abstinence. Temporal Order Memory and Working Memory tests, chemogenetic experiments as well as whole-cell patch recordings on prelimbic PFC ex vivo slices were performed during abstinence. RESULTSWe find here that repeated METH administration in rats produces deficits in working memory and increases in inhibitory synaptic transmission onto pyramidal neurons in the prefrontal cortex (PFC). The increased PFC inhibition is detected by an increase in spontaneous and evoked inhibitory postsynaptic synaptic currents (IPSCs), an increase in GABAergic presynaptic function, and a shift in the excitatory-inhibitory balance onto PFC deep-layer pyramidal neurons. We find that pharmacological blockade of D1 dopamine receptor function reduces the METH-induced augmentation of IPSCs, suggesting a critical role for D1 dopamine signaling in METH-induced hypofrontality. In addition, chronic METH administration increases the intrinsic excitability of parvalbumin-positive interneurons, a key local interneuron population in PFC that controls inhibitory tone. Using a cell type-specific chemogenetic approach, we show that increasing PV+FSI activity in the PFC is necessary and sufficient to cause deficits in temporal order memory similar to those induced by METH. CONCLUSIONTogether, our findings reveal that chronic METH exposure increases PFC inhibitory tone through a D1 dopamine signaling-dependent potentiation of inhibitory synaptic transmission, and that reduction of PV+FSI activity can rescue METH-induced cognitive deficits, suggesting a potential therapeutic approach to treating cognitive symptoms in patients suffering from methamphetamine use disorder.