Projection neurons from medial entorhinal cortex to basolateral amygdala are critical for the retrieval of morphine withdrawal memory.

The medial entorhinal cortex (MEC) is crucial for contextual memory, yet its role in context-induced retrieval of morphine withdrawal memory remains unclear. This study investigated the role of the MEC and its projection neurons from MEC layer 5 to the basolateral amygdala (BLA) (MEC-BLA neurons) in context-induced retrieval of morphine withdrawal memory. Results show that context activates the MEC in morphine withdrawal mice, and the inactivation of the MEC inhibits context-induced retrieval of morphine withdrawal memory. At neural circuits, context activates MEC-BLA neurons in morphine withdrawal mice, and the inactivation of MEC-BLA neurons inhibits context-induced retrieval of morphine withdrawal memory. But MEC-BLA neurons are not activated by conditioning of context and morphine withdrawal, and the inhibition of MEC-BLA neurons do not influence the coupling of context and morphine withdrawal memory. These results suggest that MEC-BLA neurons are critical for the retrieval, but not for the formation, of morphine withdrawal memory.

Formation of chronic morphine withdrawal memories requires C1QL3-mediated regulation of PSD95 in the mouse basolateral amygdala.

Chronic morphine withdrawal memory formation is a complex process influenced by various molecular mechanisms. In this study, we aimed to investigate the contributions of the basolateral amygdala (BLA) and complement component 1, q subcomponent-like 3 (C1QL3), a secreted and presynaptically targeted protein, to the formation of chronic morphine (repeat dosing of morphine) withdrawal memory using conditioned place aversion (CPA) and chemogenetic methods. We conducted experiments involving the inhibition of the BLA during naloxone-induced withdrawal to assess its impact on CPA scores, providing insights into the significance of the BLA in the chronic morphine memory formation process. We also examined changes in C1ql3/C1QL3 expression within the BLA following conditioning. Immunofluorescence analysis revealed the colocalization of C1QL3 and the G protein-coupled receptor, brain-specific angiogenesis inhibitor 3 (BAI3) in the BLA, supporting their involvement in synaptic development. Moreover, we downregulated C1QL3 expression in the BLA to investigate its role in chronic morphine withdrawal memory formation. Our findings revealed that BLA inhibition during naloxone-induced withdrawal led to a significant reduction in CPA scores, confirming the critical role of the BLA in this memory process. Additionally, the upregulation of C1ql3 expression within the BLA postconditioning suggested its participation in withdrawal memory formation. The colocalization of C1QL3 and BAI3 in the BLA further supported their involvement in synaptic development. Furthermore, downregulation of C1QL3 in the BLA effectively hindered chronic morphine withdrawal memory formation, emphasizing its pivotal role in this process. Notably, we identified postsynaptic density protein 95 (PSD95) as a potential downstream effector of C1QL3 during chronic morphine withdrawal memory formation. Blocking PSD95 led to a significant reduction in the CPA score, and it appeared that C1QL3 modulated the ubiquitination-mediated degradation of PSD95, resulting in decreased PSD95 protein levels. This study underscores the importance of the BLA, C1QL3 and PSD95 in chronic morphine withdrawal memory formation. It provides valuable insights into the underlying molecular mechanisms, emphasizing their significance in this intricate process.

Different projection neurons of basolateral amygdala participate in the retrieval of morphine withdrawal memory with diverse molecular pathways.

Context-induced retrieval of drug withdrawal memory is one of the important reasons for drug relapses. Previous studies have shown that different projection neurons in different brain regions or in the same brain region such as the basolateral amygdala (BLA) participate in context-induced retrieval of drug withdrawal memory. However, whether these different projection neurons participate in the retrieval of drug withdrawal memory with same or different molecular pathways remains a topic for research. The present results showed that (1) BLA neurons projecting to the prelimbic cortex (BLA-PrL) and BLA neurons projecting to the nucleus accumbens (BLA-NAc) participated in context-induced retrieval of morphine withdrawal memory; (2) there was an increase in the expression of Arc and pERK in BLA-NAc neurons, but not in BLA-PrL neurons during context-induced retrieval of morphine withdrawal memory; (3) pERK was the upstream molecule of Arc, whereas D1 receptor was the upstream molecule of pERK in BLA-NAc neurons during context-induced retrieval of morphine withdrawal memory; (4) D1 receptors also strengthened AMPA receptors, but not NMDA receptors, -mediated glutamatergic input to BLA-NAc neurons via pERK during context-induced retrieval of morphine withdrawal memory. These results suggest that different projection neurons of the BLA participate in the retrieval of morphine withdrawal memory with diverse molecular pathways.

Nucleus accumbens circuit disinhibits lateral hypothalamus glutamatergic neurons contributing to morphine withdrawal memory in male mice.

The lateral hypothalamus (LH) is physiologically critical in brain functions. The LH also plays an important role in drug addiction. However, neural circuits underlying LH involvement of drug addiction remain obscure. In the present study,our results showed that in male mice, during context-induced expression of morphine withdrawal memory, LH glutamatergic neurons played an important role; dopamine D1 receptor-expressing medium spiny neurons (D1-MSNs) projecting from the core of nucleus accumbens (NAcC) to the LH were an important upstream circuit to activate LH glutamatergic neurons; D1-MSNs projecting from the NAcC to the LH activated LH glutamatergic neurons through inhibiting LH local gamma-aminobutyric acid (GABA) neurons. These results suggest that disinhibited LH glutamatergic neurons by neural circuits from the NAcC importantly contribute to context-induced the expression of morphine withdrawal memory.

Two kinds of transcription factors mediate chronic morphine-induced decrease in miR-105 in medial prefrontal cortex of rats.

Chronic morphine administration alters gene expression in different brain regions, an effect which may contribute to plastic changes associated with addictive behavior. This change in gene expression is most possibly mediated by addictive drug-induced epigenetic remodeling of gene expression programs. Our previous studies showed that chronic morphine-induced decrease of miR-105 in the medial prefrontal cortex (mPFC) contributed to context-induced retrieval of morphine withdrawal memory. However, how chronic morphine treatment decreases miR-105 in the mPFC still remains unknown. The present study shows that chronic morphine induces addiction-related change in miR-105 in the mPFC via two kinds of transcription factors: the first transcription factor is CREB activated by mu receptors-ERK-p90RSK signaling pathway and the second transcription factor is glucocorticoid receptor (GR), which as a negative transcription factor, mediates chronic morphine-induced decrease in miR-105 in the mPFC of rats.

Inputs from paraventricular nucleus of thalamus and locus coeruleus contribute to the activation of central nucleus of amygdala during context-induced retrieval of morphine withdrawal memory.

Drug relapse can be mainly ascribed to the retrieval of drug withdrawal memory induced by conditioned context. Previous studies have shown that the central nucleus of the amygdala lateral division (CeL) could be activated by conditioned context. However, what source of input that activates the CeL during conditioned context-induced retrieval of morphine-withdrawal memory remains unknown. In this study, using retrograde labeling, immunohistochemistry, local microinjection and chemogenetic technologies, we found that (1) Conditioned context induced an activation of the CeL and the inhibition of the CeL inhibited the context-induced retrieval of morphine-withdrawal memory; (2) the inhibition of the paraventricular nucleus of thalamus (PVT) or PVT-CeL projection neurons caused an attenuation of the activation of the CeL by conditioned context and conditioned place aversion (CPA); (3) the inhibition of the locus coeruleus (LC) or LC-CeL projection neurons decreased the activation of the CeL by conditioned context and CPA. These results suggest that the CeL is necessary for conditioned context-induced retrieval of morphine-withdrawal memory and inputs from PVT and LC contribute to the activation of the CeL during context-induced retrieval of morphine withdrawal memory.