Plantinga L C, Verhaagen J, Edwards P M, Schrama L H, Burbach J P, Gispen W H
Rudolf Magnus Institute, Department of Pharmacology, Utrecht University, The Netherlands.
Brain Res Mol Brain Res. 1992 Nov;16(1-2):135-42. doi: 10.1016/0169-328x(92)90203-n.
Neuropeptides related to alpha-melanocyte-stimulating hormone (alpha-MSH) stimulate nerve outgrowth following peripheral nerve injury and may play an important physiological role in peripheral nerve regeneration. The mechanism of action underlying the neurotrophic effect of pharmacologically administered alpha-MSH is unknown. Here we investigate the hypothesis that reexpression of the proopiomelanocortin (POMC) gene, the prohormone of alpha-MSH/adrenocorticotropic hormone (ACTH)-like peptides, is part of the endogenous repertoire of peripheral nerve responses following injury. The effect of sciatic nerve crush on the expression of POMC mRNA between 0.5 h and 14 days after crush was investigated using polymerase chain reaction (PCR) and Northern blot analysis. The presence of a POMC transcript in dorsal root ganglia (DRG), spinal cord and in the sciatic nerve at the crush site could be demonstrated in both control and lesioned animals by PCR using primers located in exon 1 and 3 of the POMC gene. Minute quantities of two POMC transcripts (1200 nt and 800 nt) could be detected by Northern blot analysis of total RNA prepared from DRG, spinal cord and the sciatic nerve of control animals and of animals subjected to nerve crush. POMC mRNA expression was, however, not increased following nerve crush. Probes specific for exons 1 and 2 or specific for exon 3 of the POMC gene were employed to demonstrate that the 800 nt transcript represents the truncated POMC mRNA previously shown to be present in extra-pituitary tissue. The larger 1200 nt transcript comigrates with the full length POMC mRNA expressed in the pituitary gland. The present results demonstrate the expression of small amounts of POMC mRNA in all compartments of the sciatic nerve. The absence of an induction of POMC expression in response to nerve crush suggests that the stimulating effect of exogenously applied alpha-MSH does not mimic a POMC derived neurotrophic peptide induced in the nerve following nerve injury.
与α-黑素细胞刺激素（α-MSH）相关的神经肽可刺激周围神经损伤后的神经生长，并可能在周围神经再生中发挥重要的生理作用。药理学给予的α-MSH的神经营养作用的潜在作用机制尚不清楚。在这里，我们研究了以下假设：阿片促黑素皮质素原（POMC）基因（α-MSH/促肾上腺皮质激素（ACTH）样肽的前体激素）的重新表达是损伤后周围神经反应的内源性组成部分。使用聚合酶链反应（PCR）和Northern印迹分析研究了坐骨神经挤压对挤压后0.5小时至14天POMC mRNA表达的影响。通过使用位于POMC基因外显子1和3中的引物进行PCR，在对照动物和损伤动物中均可以证明在背根神经节（DRG）、脊髓和挤压部位的坐骨神经中存在POMC转录本。通过对从对照动物和遭受神经挤压的动物的DRG、脊髓和坐骨神经制备的总RNA进行Northern印迹分析，可以检测到微量的两种POMC转录本（1200 nt和800 nt）。然而，神经挤压后POMC mRNA表达并未增加。使用针对POMC基因外显子1和2或外显子3的特异性探针来证明800 nt转录本代表先前显示存在于垂体外组织中的截短的POMC mRNA。较大的1200 nt转录本与垂体中表达的全长POMC mRNA一起迁移。目前的结果证明了坐骨神经所有部分中少量POMC mRNA的表达。对神经挤压无POMC表达诱导表明，外源性应用的α-MSH的刺激作用并不模拟神经损伤后神经中诱导的POMC衍生的神经营养肽。
