Isolation of large dense core vesicles to investigate the mechanisms controlling the peptidergic neurotransmitter release.

P物质（substance P，SP）是一种具有生物活性的十一肽，是一种神经递质，通过初级传入神经元将有害信息从外周组织传递到中枢。SP在背根神经节（DRG）中生物合成，背根神经节是初级传入神经元的神经元索马，并且通过伤害性刺激从脊髓背角中的神经元末端释放。为阐明该肽的释放机制，在原代培养的大鼠DRG细胞上研究了神经营养因子或白细胞介素1 β（IL-1 β）对SP合成和释放的影响。神经生长因子（NGF）通过增加DRG细胞中β-和γ- PPT mRNA的转录活性来增加SP含量。IL-1 β是由免疫细胞合成和释放的细胞因子之一，被认为是炎症和痛觉过敏过程中的重要介质。当重组小鼠IL-1 β在NGF存在下加入DRG细胞中时，IL-1 β在3 h后引起SP释放。IL-1 β ft对SP释放的影响是Ca^<2+>依赖性的，并可被IL-1受体拮抗剂和环氧合酶抑制剂显著抑制。IL-1 β ft在孵育1小时后可增加诱导型环氧合酶（考克斯）-2 mRNA的表达，而对组成型考克斯-1无影响，提示IL-1 β ft通过特异性IL-1受体诱导DRG细胞释放这种伤害性神经肽，其机制可能与前列腺素系统有关。它可能与初级传入神经元到脊髓通路的炎性痛有关。

A bioactive undecapeptide, substance P (SP) is a neurotransmitter to convey noxious informations from peripheral tissues to the central nervous system through a primary afferent neuron. SP is bio-synthesized in a dorsal root ganglion (DRG) which is a neuronal soma of a primary afferent neuron and released from a neuronal terminal in the dorsal horn of a spinal cord by noxious stimuli. To elucidate the mechanisms controlling the release of this peptide, the effects of neurotrophins or interleukin-1beta (IL-1beta) on SP synthesis and release were investigated in the primary cultured rat DRG cells.SP is bio-synthesized by three kinds of isoforms of SP precursors, preprotachykinin (PPT) mRNA (alpha-, beta- and gamma-). Nerve growth factor (NGF) increased SP content by increased transcriptional activity of beta- and gamma- PPT mRNA in the DRG cells. IL-1beta is one of the cytokines which are synthesized and released from immune cells and considered to be important mediators during inflammation and hyperalgesia. When recombinant mouse IL-1beta was added to the DRG cells in the presence of NGF, IL-1beta evoked the SP release after 3 hours. The effect of IL-1beta ft on the SP release was Ca^<2+> dependent and significantly inhibited by a IL-1 receptor antagonist and cyclooxygenase inhibitors. Furthermore IL-1BETA increased inducible cyclooxygenase (COX)-2 mRNA without any effects on constitutive COX-1 in the incubation of 1 hour.Thus, it is suggested that IL-1beta ft evoked the release of this nociceptive neuropeptide in the DRG cells via specific IL-1 receptors, the mechanisms of which might be involved in prostanoid systems. It could be responsible for the hyperalgesic action with reference to inflammatory pain in primary afferent neuron to spinal cord pathway.