Graduate College of Biomedical Sciences, Western University of Health Sciences, Pomona, California, USA.
College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, California, USA.
Neuroendocrinology. 2021;111(1-2):45-69. doi: 10.1159/000506367. Epub 2020 Feb 7.
We examined whether pituitary adenylate cyclase-activating polypeptide (PACAP) excites proopiomelanocortin (POMC) neurons via PAC1 receptor mediation and transient receptor potential cation (TRPC) channel activation.
Electrophysiological recordings were done in slices from both intact male and ovariectomized (OVX) female PACAP-Cre mice and eGFP-POMC mice.
In recordings from POMC neurons in eGFP-POMC mice, PACAP induced a robust inward current and increase in conductance in voltage clamp, and a depolarization and increase in firing in current clamp. These postsynaptic actions were abolished by inhibitors of the PAC1 receptor, TRPC channels, phospholipase C, phosphatidylinositol-3-kinase, and protein kinase C. Estradiol augmented the PACAP-induced inward current, depolarization, and increased firing, which was abrogated by estrogen receptor (ER) antagonists. In optogenetic recordings from POMC neurons in PACAP-Cre mice, high-frequency photostimulation induced inward currents, depolarizations, and increased firing that were significantly enhanced by Gq-coupled membrane ER signaling in an ER antagonist-sensitive manner. Importantly, the PACAP-induced excitation of POMC neurons was notably reduced in obese, high-fat (HFD)-fed males. In vivo experiments revealed that intra-arcuate nucleus (ARC) PACAP as well as chemogenetic and optogenetic stimulation of ventromedial nucleus (VMN) PACAP neurons produced a significant decrease in energy intake accompanied by an increase in energy expenditure, effects blunted by HFD in males and partially potentiated by estradiol in OVX females.
These findings reveal that the PACAP-induced activation of PAC1 receptor and TRPC5 channels at VMN PACAP/ARC POMC synapses is potentiated by estradiol and attenuated under conditions of diet-induced obesity/insulin resistance. As such, they advance our understanding of how PACAP regulates the homeostatic energy balance circuitry under normal and pathophysiological circumstances.
我们研究了垂体腺苷酸环化酶激活肽（PACAP）是否通过 PAC1 受体介导和瞬时受体电位阳离子（TRPC）通道激活来兴奋 proopiomelanocortin（POMC）神经元。
在完整雄性和去卵巢（OVX）雌性 PACAP-Cre 小鼠和 eGFP-POMC 小鼠的切片中进行电生理记录。
在 eGFP-POMC 小鼠的 POMC 神经元记录中，PACAP 在电压钳时诱导强内向电流和电导增加，在电流钳时诱导去极化和放电增加。这些突触后作用被 PAC1 受体抑制剂、TRPC 通道、磷脂酶 C、磷脂酰肌醇 3-激酶和蛋白激酶 C 所消除。雌二醇增强了 PACAP 诱导的内向电流、去极化和放电增加，而雌激素受体（ER）拮抗剂则消除了这种作用。在 PACAP-Cre 小鼠的 POMC 神经元的光遗传学记录中，高频光刺激诱导内向电流、去极化和放电增加，这些增加以 ER 拮抗剂敏感的方式被 Gq 偶联膜 ER 信号显著增强。重要的是，肥胖、高脂肪（HFD）喂养雄性动物的 POMC 神经元中 PACAP 诱导的兴奋显著减少。体内实验表明，弓状核（ARC）PACAP 以及腹内侧核（VMN）PACAP 神经元的化学遗传学和光遗传学刺激显著降低了能量摄入，同时增加了能量消耗，这些作用在雄性 HFD 中被削弱，在 OVX 雌性中部分被雌二醇增强。
这些发现表明，VMN PACAP/ARC POMC 突触处 PAC1 受体和 TRPC5 通道的 PACAP 诱导激活被雌二醇增强，并在饮食诱导的肥胖/胰岛素抵抗条件下减弱。因此，它们增进了我们对 PACAP 在正常和病理生理情况下如何调节稳态能量平衡回路的理解。
