Impulsive action can be measured using rat’s responses on a differential reinforcement of low-rate-response (DRL) task in which performance may be varied between rats. Nevertheless, neurobiological profiles underlying the trait impulsivity of DRL behavior remain largely unknown. Here, in vivo non-invasive proton magnetic resonance spectroscopy (¹H-MRS) and Western blot assay were performed to assess neurobiological changes in the dorsal striatum (DS) and nucleus accumbens (NAc) in relation to individual differences in DRL behavior. A cohort of rats was subjected to acquire a DRL task over 14 daily sessions. High impulsive (HI) and low impulsive (LI) rats were screened by behavioral measures displaying a lower response efficiency and performing more nonreinforced responses in HI rats and vice versa. MRS measurements indicated that the HI group had a lower NAc glutamate (Glu) level than did the LI group, whereas no such difference was found in the other five metabolites in this area. Moreover, no intergroup difference was observed in any metabolite in the DS. The results of Western blot assay revealed that protein expressions of GluN1 (but not GluN2B) subunit of N-methyl-D-aspartate receptors in the DS and NAc were higher in the HI group than in the LI group. This inherent timing impulsivity was not attributed to risky behavioral propensity because both Hl and LI rats could acquire a risk-dependent choice. The findings of this study, supported by certain correlations among behavioral, brain imaging, and neuroreceptor indices, provide evidence of the neurobiological changes of striatal Glu underlying trait impulsive action of DRL behavior.

可以使用大鼠对低速率反应 (DRL) 任务的差异强化的反应来测量冲动行为，其中大鼠之间的表现可能有所不同。然而，作为 DRL 行为特征冲动背后的神经生物学特征在很大程度上仍然未知。在这里，体内非侵入性质子磁共振波谱（¹进行 H-MRS) 和蛋白质印迹测定以评估背侧纹状体 (DS) 和伏隔核 (NAc) 的神经生物学变化与 DRL 行为的个体差异有关。一组大鼠每天接受 14 次 DRL 任务。高冲动 (HI) 和低冲动 (LI) 大鼠通过行为测量进行筛选，显示出较低的反应效率和在 HI 大鼠中执行更多的非强化反应，反之亦然。MRS 测量表明，HI 组的 NAc 谷氨酸 (Glu) 水平低于 LI 组，而在该区域的其他五种代谢物中没有发现这种差异。此外，DS 中的任何代谢物均未观察到组间差异。Western blot结果显示，HI组DS和NAc中N-甲基-D-天冬氨酸受体GluN1（但不是GluN2B）亚基的蛋白表达高于LI组。这种固有的时间冲动不归因于风险行为倾向，因为 H1 和 LI 大鼠都可以获得风险依赖的选择。这项研究的结果得到了行为、脑成像和神经受体指数之间的某些相关性的支持，为纹状体 Glu 的神经生物学变化提供了证据，证明了 DRL 行为的潜在特质冲动行为。