Graduate Program of Neuroscience, The University of Western Ontario, London, N6A 5B7, Canada.
Robarts Research Institute, London, N6A 5B7, Canada.
Cerebellum. 2023 Dec;22(6):1200-1215. doi: 10.1007/s12311-022-01493-2. Epub 2022 Nov 19.
The cerebellum is a major site of endocannabinoid (eCB) production and signaling. The predominant eCB within the cerebellum, 2-arachidonoylglycerol (2-AG), is produced by a metabotropic glutamate receptor type 1 (mGluR1)-initiated signaling cascade within Purkinje neurons (PNs). 2-AG retrogradely stimulates cannabinoid 1 receptors (CB1Rs) located on presynaptic terminals. The activated CB1R decreases neurotransmitter release and leads to the production of nitric oxide (NO), a gaseous molecule. Recently, our group discovered that during development in mice lacking neuronal nitric oxide synthase (nNOS), PNs display an excitotoxic phenotype associated with overactivated mGluR1. Considering the importance of mGluR1 in 2-AG synthesis, the present study explored the role of nNOS-derived NO in regulating the eCB pathway within the cerebella of wildtype (WT) and nNOS mice at postnatal day 7 (PD7), 2 weeks (2 W), and 7 weeks (7 W). Our analysis showed that diacylglycerol lipase α, the enzyme that catalyzes 2-AG production, was elevated at early postnatal ages, and followed by elevated levels of 2-AG in nNOS cerebella compared to WT. CB1R expression in nNOS cerebella was upregulated at PD7 but decreased at 2 W and 7 W when compared to age-matched WT mice cerebella. Importantly, treating organotypic nNOS cerebellar slice cultures with an NO-donor-attenuated CB1R levels after 7 days in vitro. In addition, expression of the eCB hydrolases fatty acid amide hydrolase and monoacylglycerol lipase were significantly downregulated in nNOS cerebella compared to WT cerebella at 7 W. Together, these results reveal a novel role for nNOS/NO in regulating eCB signaling in the cerebellum.
小脑是内源性大麻素（eCB）产生和信号传递的主要部位。小脑内主要的 eCB，2-花生四烯酸甘油（2-AG），由代谢型谷氨酸受体 1（mGluR1）在浦肯野神经元（PNs）中引发的信号级联产生。2-AG 逆行刺激位于突触前末端的大麻素 1 受体（CB1R）。激活的 CB1R 减少神经递质释放，并导致产生一氧化氮（NO），一种气体分子。最近，我们的小组发现，在缺乏神经元型一氧化氮合酶（nNOS）的小鼠发育过程中，PNs 表现出与过度激活的 mGluR1 相关的兴奋性毒性表型。考虑到 mGluR1 在 2-AG 合成中的重要性，本研究探讨了 nNOS 衍生的 NO 在调节 WT 和 nNOS 小鼠出生后第 7 天（PD7）、2 周（2W）和 7 周（7W）小脑内 eCB 通路中的作用。我们的分析表明，二酰基甘油脂肪酶α，即催化 2-AG 产生的酶，在出生后早期升高，随后 nNOS 小脑中的 2-AG 水平升高，与 WT 相比。nNOS 小脑中的 CB1R 表达在 PD7 时上调，但与年龄匹配的 WT 小鼠小脑相比，在 2W 和 7W 时降低。重要的是，用一氧化氮供体处理体外培养 7 天后的 nNOS 小脑切片，降低了 CB1R 水平。此外，与 WT 小脑相比，nNOS 小脑中 eCB 水解酶脂肪酸酰胺水解酶和单酰基甘油脂肪酶的表达在 7W 时显著下调。综上所述，这些结果揭示了 nNOS/NO 在调节小脑内 eCB 信号传递中的新作用。
