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

Abstract

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.

Analysis of synaptic bodies in the Sprague–Dawley rat pineal gland under extreme photoperiods

“…Adult male cotton rats were kept under LD 8:16 (n = 5) or LD 16:8 (n = 5) by Karasek et al (1986). Animals kept in the short photoperiod showed larger relative volumes of mitochondria, RER, ribosomes, Golgi apparatuses, inclusion bodies (characteristic only for this rat strain) and dense core vesicles which can be interpreted as characteristic for higher active cells, compared to the LD 16:8 animals.…”