Memory retrieval in addiction: a role for miR-105-mediated regulation of D1 receptors in mPFC neurons projecting to the basolateral amygdala.
BACKGROUND
Drug addiction is a chronic brain disorder characterized by the compulsive use of drugs. The study of chronic morphine-induced adaptation in the brain and its functional significance is of importance to understand the mechanism of morphine addiction. Previous studies have found a number of chronic morphine-induced adaptive changes at molecular levels in the brain. A study from our lab showed that chronic morphine-induced increases in the expression of D1 receptors at presynaptic terminals coming from other structures to the basolateral amygdala (BLA) played an important role in environmental cue-induced retrieval of morphine withdrawal memory. However, the neurocircuitry where the increased D1 receptors are located and how chronic morphine increases D1 receptor expression in specific neurocircuits remain to be elucidated.


RESULTS
Our results show that chronic morphine induces a persistent increase in D1 receptor expression in glutamatergic terminals of projection neurons from the medial prefrontal cortex (mPFC) to the BLA, but has no influence on D1 receptor expression in projection neurons from the hippocampus or the thalamus to the BLA. This adaptation to chronic morphine is mediated by reduced expression of miR-105 in the mPFC, which results in enhanced D1 receptor expression in glutamatergic terminals of projection neurons from the mPFC to the BLA. Ex vivo optogenetic experiments show that a chronic morphine-induced increase in D1 receptor expression in glutamatergic terminals of projection neurons from the mPFC to the BLA results in sensitization of the effect of D1 receptor agonist on presynaptic glutamate release. mPFC to BLA projection neurons are activated by withdrawal-associated environmental cues in morphine-withdrawal rats, and overexpression of miR-105 in the mPFC leads to reduced D1 receptor induction in response to chronic morphine in glutamatergic terminals of the projection neurons from the mPFC to the BLA, and a reduction in place aversion conditioned by morphine withdrawal.


CONCLUSIONS
These results suggest that chronic morphine use induces a persistent increase in D1 receptors in glutamatergic terminals of projection neurons from the mPFC to the BLA via downregulation of miR-105 in the mPFC, and that these adaptive changes contribute to environmental cue-induced retrieval of morphine withdrawal memory.
['Zhao|Yanfang|Y|', 'Zhang|Junfang|J|', 'Yang|Hualan|H|', 'Cui|Dongyang|D|', 'Song|Jiaojiao|J|', 'Ma|Qianqian|Q|', 'Luan|Wenjie|W|', 'Lai|Bin|B|', 'Ma|Lan|L|', 'Chen|Ming|M|', 'Zheng|Ping|P|']
D000818:Animals D066272:Basolateral Nuclear Complex D005786:Gene Expression Regulation D008568:Memory D035683:MicroRNAs D009020:Morphine D009294:Narcotics D009474:Neurons D051381:Rats D017447:Receptors, Dopamine D1 D013375:Substance Withdrawal Syndrome D019966:Substance-Related Disorders
D1 receptors Basolateral amygdala Morphine Medial prefrontal cortex miR-105 Opiate withdrawal memory