Opiates produce a strong rewarding effect, but abstinence from opiate use emerges with severe negative emotions. Depression is one of the most frequent emotion disorders associated with opiate abstinence, which is thought to be a main cause for relapse. However, neurobiological bases of such an aversive emotion processing are poorly understood. Here, we find that morphine abstinence activates κ-opioid receptors (KORs) by increasing endogenous KOR ligand dynorphin expression in the amygdala, which in turn facilitates glutamate transporter 1 (GLT1) expression by activation of p38 mitogen-activated protein kinase (MAPK). Upregulation of GLT1 expression contributes to opiate-abstinence-elicited depressive-like behaviors through modulating amygdalar glutamatergic inputs to the nucleus accumbens (NAc). Intra-amygdala injection of GLT1 inhibitor DHK or knockdown of GLT1 expression in the amygdala significantly suppresses morphine-abstinence-induced depressive-like behaviors. Pharmacological and pharmacogenetic activation of amygdala-NAc projections prevents morphine-abstinence-induced behaviors. Overall, our study provides key molecular and circuit insights into the mechanisms of depression associated with opiate abstinence.
Keywords: amygdala; depression; dynorphin/κ-opioid receptor; glutamate transporter 1; morphine abstinence; nucleus accumbens.
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