RESUMO
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 IIB (NMIIB), a molecular motor that supports memory by directly driving synaptic actin polymerization. A single intra-BLC treatment with Blebbistatin (Blebb), 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, postconsolidation genetic knockdown of Myh10, the heavy chain of the most highly expressed NMII in the BLC, was sufficient to produce METH-associated memory loss. Blebb 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 24 h after a single systemic injection of Blebb delivered in the home cage. Together, these results argue for the further development of small-molecule inhibitors of NMII as potential therapeutics for the prevention of SUD relapse triggered by drug associations.
Assuntos
Transtornos Relacionados ao Uso de Anfetaminas/tratamento farmacológico , Transtornos Relacionados ao Uso de Anfetaminas/metabolismo , Tonsila do Cerebelo/efeitos dos fármacos , Fármacos do Sistema Nervoso Central/administração & dosagem , Metanfetamina/administração & dosagem , Miosina não Muscular Tipo IIB/antagonistas & inibidores , Transtornos Relacionados ao Uso de Anfetaminas/patologia , Tonsila do Cerebelo/metabolismo , Animais , Condicionamento Psicológico/efeitos dos fármacos , Condicionamento Psicológico/fisiologia , Modelos Animais de Doenças , Comportamento de Procura de Droga/efeitos dos fármacos , Comportamento de Procura de Droga/fisiologia , Comportamento Exploratório/efeitos dos fármacos , Comportamento Exploratório/fisiologia , Medo/efeitos dos fármacos , Medo/fisiologia , Técnicas de Silenciamento de Genes , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Masculino , Memória/efeitos dos fármacos , Memória/fisiologia , Camundongos , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Miosina não Muscular Tipo IIB/genética , Miosina não Muscular Tipo IIB/metabolismo , Ratos , Prevenção Secundária , Autoadministração , Comportamento Espacial/efeitos dos fármacos , Comportamento Espacial/fisiologiaRESUMO
The timeline of dopamine (DA) system maturation and the signaling properties of DA receptors (DRs) during rat brain development are not fully characterized. We used in situ hybridization and quantitative PCR to map DR mRNA transcripts in the medial frontal cortex (mFC) and striatum (STR) of the rat from embryonic day (E) 15 to E21. The developmental trajectory of DR mRNAs revealed distinct patterns of DA receptors 1 and 2 (DRD1, DRD2) in these brain regions. Whereas the mFC had a steeper increase in DRD1 mRNA, the STR had a steeper increase in DRD2 mRNA. Both DR mRNAs were expressed at a higher level in the STR compared with the mFC. To identify the functional properties of DRs during embryonic development, the phosphorylation states of cyclic AMP response element binding protein, extracellular signal-regulated kinase 1/2, and glycogen synthase kinase 3 beta were examined after DR stimulation in primary neuronal cultures obtained from E15 and E18 embryos and cultured for 3 days to ensure a stable baseline level. DR-mediated signaling cascades were functional in E15 cultures in both brain regions. Because DA fibers do not reach the mFC by E15, and DA was not present in cultures, these data indicate that DRs can become functional in the absence of DA innervation. Because activation of DR signal transduction pathways can affect network organization of the developing brain, maternal exposure to drugs that affect DR activity may be liable to interfere with fetal brain development.