title: Nerve growth factor-mediated neuronal plasticity in spinal cord contributes to neonatal maternal separation-induced visceral hypersensitivity in rats.
abstract: Visceral hyperalgesia is a multifactorial gastrointestinal disorder which featured with alterations of abdominal motility and/or gut sensitivity, and is believed to be triggered by environmental stressor or psychological factors. However, its etiology remains incompletely understood. In this study, we aimed to investigate whether nerve growth factor (NGF)-mediated neuronal plasticity is involved in neonatal maternal separation (NMS)-induced visceral hypersensitivity in adult rats, and whether NGF antagonist can attenuate or block such development. In our experiments, animals subjected to NMS were developed with visceral hyperalgesia at age of 8 weeks. The threshold for visceral pain among these NMS rats was remarkably lowered than that of the normal handling (NH) rats; however, the expression levels of NGF, c-fos, calcitonin gene-related peptide (CGRP), Substance P, and tyrosine kinases A (TrkA) were notably elevated in lumbosacral spinal cord and/or dorsal root ganglion (DRG) when comparing to those of the NH rats. Further, as intra-peritoneal administration of NGF (10 μl at 1 μg/kg/day) was given to NH rats during neonatal period, effects that comparable to NMS induction were observed in the adulthood. In contrast, when NMS rats were treated with NGF antagonist K252a (10 μl/day from postnatal days 2-14), which acts against tyrosine kinases, the neonatal stress-induced down-shifted visceral pain threshold was restored and neuronal activation, specifically NGF and neuropeptide production, was attenuated. In conclusion, our data strongly suggest that NGF triggers neuronal plasticity and plays a crucial role in NMS-induced visceral hypersensitivity in which NGF antagonism provides positive inhibition via blocking the tyrosine phosphorylation of TrkA.
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
authors.forename: S W
authors.initials: SW
authors.lastname: Tsang
authors.forename: M
authors.initials: M
authors.lastname: Zhao
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: J J Y
authors.initials: JJ
authors.lastname: Sung
authors.forename: Z-X
authors.initials: ZX
authors.lastname: Bian
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001010:Anxiety, Separation / Q000523:psychology*; D015153:Blotting, Western; D015740:Calcitonin Gene-Related Peptide / Q000096:biosynthesis; D002227:Carbazoles / Q000494:pharmacology; D005260:Female; D005455:Fluorescent Antibody Technique; D005767:Gastrointestinal Diseases / Q000523:psychology*; D006930:Hyperalgesia / Q000523:psychology*; D026121:Indole Alkaloids / Q000494:pharmacology; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy / Q000503:physiopathology; D007274:Injections, Intraperitoneal; D008297:Male; D008426:Maternal Deprivation; D020932:Nerve Growth Factor / Q000096:biosynthesis / Q000494:pharmacology*; D009473:Neuronal Plasticity / Q000187:drug effects*; D010147:Pain Measurement; D011247:Pregnancy; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor / Q000096:biosynthesis; D020917:Receptor, trkA / Q000096:biosynthesis; D013116:Spinal Cord / Q000502:physiology*; D013373:Substance P / Q000096:biosynthesis
chemical_list: D002227:Carbazoles; D026121:Indole Alkaloids; D020800:Receptor, Nerve Growth Factor; D013373:Substance P; D020932:Nerve Growth Factor; C049985:staurosporine aglycone; D011505:Protein-Tyrosine Kinases; D020917:Receptor, trkA; D015740:Calcitonin Gene-Related Peptide