Neuroscience
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Amphetamine withdrawal (AW) is accompanied by diminished pleasure and depression which plays a key role in drug relapse and addictive behaviors. There is no efficient treatment for AW-induced depression and underpinning mechanisms were not well determined. Considering both transient receptor potential cation channel, subfamily V, member 1 (TRPV1) and N-Methyl-d-aspartate (NMDA) receptors contribute to pathophysiology of mood and addictive disorders, in this study, we investigated the role of TRPV1 and NMDA receptors in mediating depressive-like behaviors following AW in male mice. ⋯ None of aforementioned treatments had any effect on behavior of control animals. Collectively, our findings showed that activation of TRPV1 and blockade of NMDA receptors produced antidepressant-like effects in male mice following AW, and these receptors are involved in AW-induced depressive-like behaviors. Further, we found that rapid antidepressant-like effects of capsaicin in FST and splash test are partly mediated by NMDA receptors.
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The bed nucleus of the stria terminalis (BNST), a nucleus defined as part of the extended amygdala, is involved in the expression of anxiety disorders. However, the regulatory mechanisms of BNST inhibitory activity that is involved in anxiety are unknown. Here, we showed that blocking neuregulin 1 (NRG1)-ErbB4 signaling in the BNST of mice, by either neutralizing endogenous NRG1 with ecto-Erbb4 or antagonizing the ErbB4 receptor with its specific inhibitor, produced anxiogenic responses. ⋯ While infusion of the GABAA receptor antagonist bicuculline into the BNST also led to anxiety-related behaviors, it did not worsen the anxiogenic effects produced by blocking NRG1-ErbB4 signaling, suggesting possible involvement of GABAergic neurotransmission. Further, in vitro electrophysiological recordings showed that BNST NRG1-ErbB4 signaling regulated the presynaptic GABA release. Together, these results suggest that NRG1-ErbB4 signaling in the BNST may play an important role in regulating anxiety-like behaviors.
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Dopamine and glutamate play critical roles in the reinforcing effects of cocaine. We demonstrated that a single intraperitoneal administration of cocaine induces a significant decrease in [(3)H]-d-aspartate uptake in the pre-frontal cortex (PFC). This decrease is associated with elevated dopamine levels, and requires dopamine D1-receptor signaling (D1R) and adenylyl cyclase activation. ⋯ This rapid response is related to D1R-mediated cAMP-mediated activation of PKA and phosphorylation of the excitatory amino acid transporters EAAT1, EAAT2 and EAAT3. We also demonstrated that cocaine exposure increases extracellular d-aspartate, l-glutamate and d-serine in the PFC. Our data suggest that cocaine activates dopamine D1 receptor signaling and PKA pathway to regulate EAATs function and extracellular EAA level in the PFC.