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

点击翻译按钮获取中文摘要

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.