Substance P-like immunoreactivity in the suprachiasmatic nucleus of the rat

Yasumasa Otori, Keiko Tominaga, Chiaki Fukuhara, Jing Yang, Shin Yamazaki, Felino Ramon A Cagampang, Hitoshi Okamura, Shin Ichi T Inouye

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28 Scopus citations


The content of substance P (SP)-like immunoreactivity (LI) within the suprachiasmatic nucleus (SCN) of rats was determined by enzyme immunoassay to evaluate the effect of light on SP-LI in the rat SCN. Male rats were kept under various lighting conditions: light-dark cycles, constant darkness, continuous light exposure for 24 h or light pulse interrupting constant darkness. Animals were also subjected to ocular enucleation. The present study showed that SP-LI in the SCN was unaffected by environmental lighting conditions or by bilateral ocular enucleation. Immunohistochemical studies also confirmed that SP immunoreactivity, which was found in the ventrolateral (VL) subdivision of the SCN, was not reduced significantly even after ocular enucleation. These results suggest that, in contrast to other neurotransmitters in the VL portion of the SCN such as vasoactive intestinal polypeptide (VIP), gastrin releasing peptide (GRP) and neuropeptide Y (NPY), SP level in the SCN is quite stable to light and arises from an area other than the retina.

Original languageEnglish (US)
Pages (from-to)271-277
Number of pages7
JournalBrain Research
Issue number1-2
StatePublished - Aug 13 1993


  • Circadian rhythm
  • Enzyme immunoassay
  • Rat
  • Retinohypothalamic tract
  • Substance P
  • Suprachiasmatic nucleus

ASJC Scopus subject areas

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


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