Effects of Long and Short Photoperiod on the Ultrastructure of Pinealocytes of the Cotton Rat (Sigmodon hispidus)

Michal Karasek, Susan A. Matthews, Thomas S. King, Russel J. Reiter

Research output: Contribution to journalArticle

8 Scopus citations


The ultrastructure of the pinealocytes of wild‐captured cotton rats (Sigmodon hispidus) housed in either long or short photoperiod was examined. Quantitative comparison of selected pinealocyte organelles revealed larger relative volumes of mitochondria, granular endoplasmic reticulum and ribosomes, Golgi apparatus, and inclusion bodies, as well as a higher number of dense‐core vesicles in the animals kept in short photoperiod (LD 8:16) as compared to those in animals kept in long photoperiod (LD 16:8). These observations suggest that restricting the amount of light to which animals are exposed activates pinealocytes of the cotton rat.

Original languageEnglish (US)
Pages (from-to)323-330
Number of pages8
JournalJournal of pineal research
Issue number4
StatePublished - Oct 1986



  • cotton rat
  • photoperiod
  • pineal gland
  • ultrastructure

ASJC Scopus subject areas

  • Endocrinology

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