Haddar Meriem, Uno Kyosuke, Hamatani Kohei, Muramatsu Shin-Ichi, Nitta Atsumi
Department of Pharmaceutical Therapy and Neuropharmacology, Faculty of Pharmaceutical Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
Laboratory of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Japan.
Neuropsychopharmacol Rep. 2019 Sep;39(3):209-216. doi: 10.1002/npr2.12068. Epub 2019 Jul 8.
We previously reported that methamphetamine (METH)-induced conditioned place preference was attenuated by Shati/Nat8l overexpression in the medial prefrontal cortex (mPFC). Shati/Nat8l overexpression in the mPFC expressed lower levels of both glutamate and dopamine (DA) in the nucleus accumbens (NAc) and attenuated METH-induced DA elevation. We suggested a mechanism in which a decline of glutamate levels in the NAc decreases extracellular DA levels. However, the hypothesis has not confirmed.
We conducted a recovery experiments by pre-microinjection of an mGluR group II antagonist, LY341495, into the NAc shell of mPFC-Shati/Nat8l-overexpressed mice followed by METH injection and DA levels measurement by in vivo microdialysis.
Pretreatment with LY341495 was able to restore METH-induced DA increase. Furthermore, mice injected with an adeno-associated virus vector containing GFP (AAV-GFP vector) in the mPFC expressed a colocalization of GFP with DARPP-32 a medium spiny neuron (MSN) marker. Next, co-immunostaining of DARPP-32 and neuronal nitric oxide synthase (nNOS: expressed in a subtype of gamma-Aminobutyric acid (GABA interneurons) in ventral tegmental area (VTA) showed a colocalization of nNOS and DARPP-32.
These results provided a proof that Shati/Nat8l attenuation of METH-induced DA increase is mediated by mGluR group II in the NAc. Moreover, immunohistochemical study showed a direct connection of mPFC projection neurons with NAc MSN and a connection of MSN projection neurons with a subtype of GABA interneurons in VTA.
我们之前报道过，内侧前额叶皮质（mPFC）中Shati/Nat8l过表达可减弱甲基苯丙胺（METH）诱导的条件性位置偏爱。mPFC中Shati/Nat8l过表达会使伏隔核（NAc）中的谷氨酸和多巴胺（DA）水平降低，并减弱METH诱导的DA升高。我们提出了一种机制，即NAc中谷氨酸水平的下降会降低细胞外DA水平。然而，这一假设尚未得到证实。
我们通过预先向mPFC-Shati/Nat8l过表达小鼠的NAc壳内微量注射II型代谢型谷氨酸受体（mGluR）拮抗剂LY341495，随后注射METH并通过体内微透析测量DA水平，进行了一项恢复实验。
LY341495预处理能够恢复METH诱导的DA增加。此外，在mPFC中注射含绿色荧光蛋白的腺相关病毒载体（AAV-GFP载体）的小鼠，其绿色荧光蛋白与中棘神经元（MSN）标记物DARPP-32共定位。接下来，对DARPP-32和神经元型一氧化氮合酶（nNOS：在腹侧被盖区（VTA）的γ-氨基丁酸（GABA）中间神经元亚型中表达）进行免疫共染色，结果显示nNOS和DARPP-32共定位。
这些结果证明，Shati/Nat8l对METH诱导的DA增加的减弱作用是由NAc中的II型mGluR介导的。此外，免疫组织化学研究显示mPFC投射神经元与NAc MSN直接相连，以及MSN投射神经元与VTA中GABA中间神经元亚型相连。
