Sun Y, Rao M S, Landis S C, Zigmond R E
Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106.
J Neurosci. 1992 Oct;12(10):3717-28. doi: 10.1523/JNEUROSCI.12-10-03717.1992.
Depolarization has been shown to alter the biosynthesis of a number of neurotransmitters and neuromodulators. In the rat superior cervical ganglion (SCG), for example, depolarization has been reported to increase catecholamine biosynthesis and to decrease the level of substance P. We have recently found that, although the level of vasoactive intestinal peptide (VIP)-like immunoreactivity (IR) is normally low in the SCG, it increases significantly 48 hr after adult ganglia are deafferented in situ or placed in organ culture. Both manipulations decrease electrical activity of postganglionic neurons. To determine whether the increases in ganglionic VIP-IR could be a consequence of decreased depolarization of sympathetic neurons, the effect of depolarization on the expression of VIP-IR was examined in organ cultures of neonatal and adult SCG. Depolarization with elevated K+ (30 mM) or veratridine (1.5 microM) amplified, rather than blocked, the increases in VIP-IR content seen after 24 hr. Further, it increased the number of detectable VIP-IR neuronal cell bodies and processes. The stimulatory effects of veratridine were prevented by TTX. Since similar changes in expression of VIP-IR were evident in dissociated cell cultures of the SCG, cell-cell interactions requiring intact ganglionic architecture are not necessary for altered peptide expression. Elevating the concentration of Mg2+ blocked the ability of K+ and veratridine to increase VIP-IR in dissociated cell culture, raising the possibility that the effects of depolarization on VIP-IR are mediated by increased Ca2+ entry. The depolarizing conditions that increased VIP-IR also increased substance P-IR. While higher concentrations of veratridine (50 microM) blocked the elevation of both VIP- and substance P-IR induced by explantation, they produced significant neuronal death. Since depolarization with either 30 mM KCl or 1.5 microM veratridine increases expression of VIP-IR in neonatal and adult ganglia, decreased depolarization is unlikely to cause the increases in VIP- and substance P-IR that occur in culture. Furthermore, our data raise the possibility that sympathetic nerve activity in vivo can increase expression of these peptides.
去极化已被证明会改变多种神经递质和神经调质的生物合成。例如，在大鼠颈上神经节（SCG）中，据报道去极化会增加儿茶酚胺的生物合成并降低P物质的水平。我们最近发现，尽管在SCG中血管活性肠肽（VIP）样免疫反应性（IR）的水平通常较低，但在成年神经节原位去传入或置于器官培养中48小时后，其显著增加。这两种操作都会降低节后神经元的电活动。为了确定神经节VIP-IR的增加是否可能是交感神经元去极化减少的结果，我们在新生和成年SCG的器官培养中研究了去极化对VIP-IR表达的影响。用高钾（30 mM）或藜芦碱（1.5 μM）去极化在24小时后放大了而非阻断了VIP-IR含量的增加。此外，它增加了可检测到的VIP-IR神经元细胞体和突起的数量。藜芦碱的刺激作用被河豚毒素（TTX）阻断。由于在SCG的解离细胞培养中VIP-IR表达的类似变化很明显，因此改变肽表达不需要完整神经节结构的细胞间相互作用。提高Mg2+浓度会阻断高钾和藜芦碱在解离细胞培养中增加VIP-IR的能力，这增加了去极化对VIP-IR的影响是由Ca2+内流增加介导的可能性。增加VIP-IR的去极化条件也增加了P物质-IR。虽然更高浓度的藜芦碱（50 μM）阻断了外植诱导的VIP-和P物质-IR的升高，但它们会导致显著的神经元死亡。由于用30 mM KCl或1.5 μM藜芦碱去极化会增加新生和成年神经节中VIP-IR的表达，去极化减少不太可能导致培养中VIP-和P物质-IR的增加。此外，我们的数据增加了体内交感神经活动可增加这些肽表达的可能性。
