Neonatal primary neuronal death induced by capsaicin and axotomy involves an apoptotic mechanism

Tomosada Sugimoto, Chun Xiao, Hiroyuki Ichikawa

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

To clarify the mechanism of capsaicin-induced primary neuronal cell death, newborn and adult rats were given a subcutaneous injection of capsaicin (50 mg/kg). Neonatal capsaicin injection induced neuronal apoptosis in the trigeminal ganglion. Apoptotic neurons had peripheral stacks of long parallel endoplasmic reticulum that are characteristic to primary neurons of the B-type, and exhibited nucleoplasmic condensation, nuclear shrinkage and cytoplasmic fragmentation. Light microscopically, apoptotic neurons exhibited a sign of DNA fragmentation as revealed by a nick end labelling method. The proportion of apoptotic cells was quite low during the first 12 h after capsaicin injection (< 1%), rapidly increase to 10.44% by 24 h, and decreased to 0.29% by 48 h. Normal and vehicle control levels of apoptosis were < 1%. Nerve growth factor (NGF, 0.5 mg/kg) simultaneously administered with capsaicin reduced the incidence of apoptosis by about 35% at 24 h post- injection. Neonatal transection of the infraorbital nerve induced neuronal apoptosis similar to that produced by the neonatal capsaicin in the maxillary division of the trigeminal ganglion. Unlike capsaicin, however, the neurotomy-induced apoptosis was seen in neurons of both the A- and B-types. Neither the capsaicin injection nor the neurotomy induced apoptosis in adult rats, though mitochondrial swelling similar to that seen at 0.5 h after neonatal capsaicin was observed after capsaicin injection in adults. The results indicate that the capsaicin-induced and nerve injury-induced primary neuronal damages in newborn rats share a common final pathway, apoptosis.

Original languageEnglish
Pages (from-to)147-154
Number of pages8
JournalBrain Research
Volume807
Issue number1-2
DOIs
Publication statusPublished - Oct 5 1998

Keywords

  • Apoptosis
  • Capsaicin
  • Nerve growth factor
  • Nerve injury
  • Primary neuron
  • Trigeminal ganglion

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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