Wild-captured cotton rats (Sigmodon hispidus) trapped and tested in September and October exhibited a rapid reduction in pineal N-acetyltransferase (NAT) activity and melatonin levels after exposure to a light irradiance of 300 ωW/cm2 during the dark period. The half-time for the depression of both NAT and melatonin was on the order of 2 min. The exposure of cotton rats during darkness to much lower irradiances of light, i.e., 5.0, 0.04, 0.03 or 0.01 W/cm2, for 32 min also greatly diminished pineal NAT activity and radioimmunoassayable melatonin levels; however, a light irradiance of 0.005 ωW/cm2 failed to significantly depress either the acetylating enzyme or the melatonin content of the pineal gland. The results show that the pineal gland of the wild-captured cotton rat, as judged by NAT activity and melatonin levels, is inhibited even by very low irradiances of light.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)