Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania.
Alcohol Clin Exp Res. 2018 Sep;42(9):1650-1660. doi: 10.1111/acer.13826. Epub 2018 Jul 20.
The paraventricular nucleus of the thalamus (PVT) is a limbic brain structure that affects ethanol (EtOH) drinking, but the neurochemicals transcribed in this nucleus that may participate in this behavior have yet to be fully characterized. The neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP), is known to be transcribed in other limbic areas and to be involved in many of the same behaviors as the PVT itself, possibly including EtOH drinking. It exists in 2 isoforms, PACAP-38 and PACAP-27, with the former expressed at higher levels in most brain regions. The purpose of this study was to characterize PACAP in the PVT and to assess its response to EtOH drinking.
First, EtOH-naïve, Sprague Dawley rats were examined using quantitative real-time polymerase chain reaction (qPCR) and immunohistochemistry, to characterize PACAP mRNA and peptide throughout the rostrocaudal axis of the PVT. Next, EtOH-naïve, vGLUT2-GFP transgenic mice were examined using immunohistochemistry, to identify the neurochemical phenotype of the PACAPergic cells in the PVT. Finally, Long Evans rats were trained to drink 20% EtOH under the intermittent-access paradigm and then examined with PCR and immunohistochemistry, to determine the effects of EtOH on endogenous PACAP in the PVT.
Gene expression of PACAP was detected across the entire PVT, denser in the posterior than the anterior portion of this nucleus. The protein isoform, PACAP-27, was present in a high percentage of cell bodies in the PVT, again particularly in the posterior portion, while PACAP-38 was instead dense in fibers. All PACAP-27 cells colabeled with glutamate, which itself was identified in the majority of PVT cells. EtOH drinking led to an increase in PACAP gene expression and in levels of PACAP-27 in individual cells of the PVT.
This study characterizes the PVT neuropeptide, PACAP, and its understudied protein isoform, PACAP-27, and demonstrates that it is involved in pharmacologically relevant EtOH drinking. This indicates that PACAP-27 should be further investigated for its possible role in EtOH drinking.
丘脑室旁核（PVT）是一个边缘脑结构，它影响乙醇（EtOH）的摄入，但该核中转录的神经化学物质可能参与这种行为尚未得到充分表征。神经肽，垂体腺苷酸环化酶激活肽（PACAP），已知在其他边缘区域被转录，并参与与 PVT 本身相同的许多行为，可能包括 EtOH 摄入。它有 2 种同工型，PACAP-38 和 PACAP-27，前者在大多数脑区表达水平更高。本研究的目的是描述 PVT 中的 PACAP，并评估其对 EtOH 摄入的反应。
首先，使用定量实时聚合酶链反应（qPCR）和免疫组织化学检查，对 Sprague Dawley 大鼠进行研究，以描述 PVT 中从头至尾的 PACAP mRNA 和肽。接下来，使用免疫组织化学检查，对 vGLUT2-GFP 转基因小鼠进行研究，以鉴定 PVT 中 PACAP 能神经元的神经化学表型。最后，用 PCR 和免疫组织化学检查，对长期摄入 20%EtOH 的 Long Evans 大鼠进行研究，以确定 EtOH 对 PVT 中内源性 PACAP 的影响。
在整个 PVT 中都检测到了 PACAP 的基因表达，后部比核的前部更密集。PACAP-27 蛋白同工型存在于 PVT 中的大量细胞体中，尤其是在后部，而 PACAP-38 则密集存在于纤维中。所有的 PACAP-27 细胞都与谷氨酸共标记，谷氨酸本身存在于 PVT 细胞的大多数细胞中。EtOH 摄入导致 PVT 中 PACAP 基因表达增加和单个细胞中 PACAP-27 水平增加。
本研究描述了 PVT 神经肽 PACAP 及其研究较少的蛋白同工型 PACAP-27，并表明其参与了药理学上相关的 EtOH 摄入。这表明 PACAP-27 应该进一步研究其在 EtOH 摄入中的可能作用。
