Shati/Nat8l is a novel N-acetyltransferase identified in the brain of mice treated with methamphetamine (METH). Shati/Nat8l mRNA is expressed in various brain areas, including the prefrontal cortex (PFC), where the expression level is higher than that in other brain regions. Shati/Nat8l overexpression in the nucleus accumbens (NAc) attenuates the pharmacological response to METH via mGluR3. Meanwhile, dopamine (DA) and glutamate dysregulations have been reported in the medial prefrontal cortex (mPFC) and NAc after METH self-administration and during reinstatement. However, the mechanism, the reward system, and function of Shati/Nat8l in the mPFC is unclear.Here, we injected an adeno-associated virus (AAV) vector containing Shati/Nat8l into the mPFC of mice, to overexpress Shati/Nat8l in the mPFC (mPFC-Shati/Nat8l). Interestingly, the METH-induced conditioned place preference (CPP) was attenuated in the mPFC-Shati/Nat8l mice, but locomotor activity was not. Additionally, immunohistochemical results from mice that were injected with AAV-GFP showed fluorescence in the mPFC and other brain regions, mainly the NAc, indicating an mPFC-NAc topdown connection. Finally, in vivo microdialysis experiments revealed that Shati/Nat8l overexpression in the mPFC reduced extracellular DA levels and suppressed the METH-induced DA increase in the NAc. Moreover, decreased extracellular glutamate levels were observed in the NAc. These results indicate that Shati/Nat8l overexpression in the mPFC attenuates METH-induced CPP by decreasing extracellular DA in the NAc. In contrast, Shati/Nat8l-mPFC overexpression did not alter METH-induced hyperlocomotion. This study demonstrates that Shati/Nat8l in the mPFC attenuates METH reward-seeking behaviour but not the psychomotor activity of METH.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Aim 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. Methods 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. Results 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. Conclusion 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.
Shati/Nat8l (Shati) is a novel N-acetyltransferase identified in the brain of mice treated with methamphetamine (METH). Recent studies showed that Shati overexpression in the nucleus accumbens (NAc) attenuates pharmacological response of methamphetamine (METH) via mGluR3. Meanwhile, it is reported that after METH self-administration and during reinstatement, dopamine (DA) and glutamate dysregulations were observed in medial PFC (mPFC) and NAc of rats. However, the regulatory mechanism of control over-reward system and the function of Shati in mPFC have not been clarified. In this study, we injected AAV-Shati vector into the mPFC of mice. Interestingly, Shati injected mice attenuated METH-induced conditioned place preference (CPP) but not locomotor activity. Additionally, immunohistochemistry of mice injected with GFP in mPFC showed an mPFC-NAc top-down regulation. Finally, in vivo microdialysis experiments showed a decrease in DA baseline and METH-induced increased DA in the NAc. Moreover, a decrease in extracellular glutamate levels was also observed in the NAc. These results suggest that Shati overexpression in mPFC attenuates METH-induced CPP by decreasing extracellular DA in the NAc.
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