Nonmuscle myosin IIB as a therapeutic target for the prevention of relapse to methamphetamine use

Abstract

Memories associated with drug use increase vulnerability to relapse in substance use disorder (SUD) and there are no pharmacotherapies for the prevention of relapse. Previously, we reported a promising finding that storage of memories associated with methamphetamine (METH), but not memories for fear or food reward, is vulnerable to disruption by actin depolymerization in the basolateral amygdala complex (BLC). However, actin is not a viable therapeutic target because of its numerous functions throughout the body. Here we report the discovery of a viable therapeutic target, nonmuscle myosin II (NMIIB), a molecular motor that supports memory by directly driving synaptic actin polymerization. A single intra-BLC treatment with Blebbistatin, a small molecule inhibitor of class II myosin isoforms, including NMIIB, produced a long-lasting disruption of context-induced drug seeking (at least 30 days). Further, post-consolidation genetic knockdown of Myh10, the heavy chain of the most highly expressed NMII in the BLC, was sufficient to produce METH-associated memory loss. Blebbistatin was found to be highly brain penetrant. A single systemic injection of the compound selectively disrupted the storage of METH-associated memory and reversed the accompanying increase in BLC spine density. This effect was specific to METH-associated memory, as it had no effect on an auditory fear memory. The effect was also independent of retrieval, as METH-associated memory was disrupted twenty-four hours after a single systemic injection of Blebbistatin delivered in the home cage. Together, these results argue for the further development of small molecule inhibitors of nonmuscle myosin II as potential therapeutics for the prevention of SUD relapse triggered by drug associations.

Nonmuscle myosin II inhibition disrupts methamphetamine-associated memory in females and adolescents

“…Anesthesia, BLC cannulation, intra-jugular catheterization and post-operative care were performed as previously described [12, 13]. Briefly, rats were implanted bilaterally with 26G guide cannulae (Plastics One) 2mm above the BLC (lateral and basolateral nuclei; AP −2.9 mm, ML +5 mm relative to bregma; DV −6.7 mm from skull, (Paxino & Watson)).…”

“…Self-administration training procedures and animal care were conducted as previously described [12, 13]. Rats underwent 20 hrs of FR1 food training prior to jugular catheterization and BLC cannulation.…”

“…Evidence from our group suggests that, unlike LTP and memories associated with fear and food reward, the F-actin supporting METH-associated memories remains dynamic long after learning within the BLC, a subregion of the brain’s emotional memory center [9, 10, 12, 13]. This renders METH-associated memories selectively vulnerable to disruption by actin depolymerization days to weeks after learning.…”

“…Therefore, we shifted focus upstream of actin polymerization to the molecular motor nonmuscle myosin II (NMII), which we have previously demonstrated to have a critical and temporally restricted role in synaptic actin polymerization and fear memory [9, 10]. As with targeting actin polymerization directly, inhibiting NMII with a single infusion of Blebb, the small molecular inhibitor of NMII, in the BLC immediately disrupted METH-associated memories in adult males, without the need for retrieval and continued to prevent drug seeking behavior for at least one month [13]. Importantly, we have found that systemic injections of Blebb are tolerated by rodents.…”

“…Importantly, we have found that systemic injections of Blebb are tolerated by rodents. Furthering this, we found that Blebb is highly brain penetrant, enabling systemic injections to disrupt METH-associated memories and reverse the associated changes in BLC spine density [13]. …”