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Mu‐opioid receptors in septum mediate the development of behavioural sensitization to a single morphine exposure in male rats
Author(s) -
Li YuLing,
Wei Shoupeng,
Liu Qing,
Gong Qi,
Zhang QingJie,
Zheng TianGe,
Yong Zheng,
Chen Feng,
Lawrence Andrew J.,
Liang JianHui
Publication year - 2022
Publication title -
addiction biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.445
H-Index - 78
eISSN - 1369-1600
pISSN - 1355-6215
DOI - 10.1111/adb.13066
Subject(s) - microinjections , opioid , morphine , sensitization , chemistry , microinjection , pharmacology , receptor , dopamine , septal nuclei , opioid receptor , medicine , endocrinology , neuroscience , central nervous system , biology
Behavioural sensitization (BS) is characterized by enhanced psychomotor responses to a dose of substance of abuse after prior repeated exposure. We previously reported that BS can be induced by a single injection of morphine in rats, whereas septal nuclei are specifically involved in the development phase of BS. Here, we demonstrated that intra‐LS or intra‐MS microinjections also incubated BS to a systemic morphine injection in a cross‐sensitization fashion, whereas inactivation of either subdivision of septal nuclei (LS: lateral septum; MS: medial septum) can negate this ability of morphine. Then, non‐selective (naloxone) and selective (μ‐, δ‐ and κ‐)opioid receptor antagonists were directly delivered into LS or MS, respectively, ahead of a morphine microinjection, whereas only μ‐opioid receptors in both LS and MS play indispensable roles in mediating the BS development. Finally, there was a pronounced elevation in the levels of the monoamines (i.e. dopamine, homovanillic acid, 5‐hydroxytryptamine and 5‐hydroxyindoleacetic acid) in the septum, 8 h after a morphine injection detected with a HPLC‐ECD method, suggesting that dopaminergi and serotoninergic systems are implicated in the BS formation. Our studies demonstrated that septal nuclei critically participate in the BS development. Essentially, μ‐ instead of δ‐ or κ‐opioid receptors in LS and MS mediate sensitization to opiates.