M1 muscarinic activation induces long-lasting increase in intrinsic excitability of striatal projection neurons

•Cholinergic activation induces persistent increase in excitability of dorsolateral striatal MSNs.•It is associated with negative shift of AP threshold, decrease in AHP amplitude and increase in EPSP-AP coupling.•M1 mAChR antagonist VU0255035 prevents the persistent increase in MSN excitability.•M1 PAM VU0453595 potentiates the persistent increase in MSN excitability.•VU0453595 enhances performance of mice in cue-dependent water-based T-maze.

The dorsolateral striatum is critically involved in movement control and motor learning. Striatal function is regulated by a variety of neuromodulators including acetylcholine. Previous studies have shown that cholinergic activation excites striatal principal projection neurons, medium spiny neurons (MSNs), and this action is mediated by muscarinic acetylcholine subtype 1 receptors (M1) through modulating multiple potassium channels. In the present study, we used electrophysiology techniques in conjunction with optogenetic and pharmacological tools to determine the long-term effects of striatal cholinergic activation on MSN intrinsic excitability. A transient increase in acetylcholine release in the striatum by optogenetic stimulation resulted in a long-lasting increase in excitability of MSNs, which was associated with hyperpolarizing shift of action potential threshold and decrease in afterhyperpolarization (AHP) amplitude, leading to an increase in probability of EPSP-action potential coupling. The M1 selective antagonist VU0255035 prevented, while the M1 selective positive allosteric modulator (PAM) VU0453595 potentiated the cholinergic activation-induced persistent increase in MSN intrinsic excitability, suggesting that M1 receptors are critically involved in the induction of this long-lasting response. This M1 receptor-dependent long-lasting change in MSN intrinsic excitability could have significant impact on striatal processing and might provide a novel mechanism underlying cholinergic regulation of the striatum-dependent motor learning and cognitive function. Consistent with this, behavioral studies indicate that potentiation of M1 receptor signaling by VU0453595 enhanced performance of mice in cue-dependent water-based T-maze, a dorsolateral striatum-dependent learning task.