Non-suppressibility by room light of pineal N-acetyltransferase activity and melatonin levels in two diurnally active rodents, the Mexican ground squirrel (Spermophilus mexicanus) and the eastern chipmunk (Tamias striatus).
The rhythms in pineal N-acetyltransferase (NAT) activity and melatonin levels were studied in the diurnally active Mexican ground squirrel and Eastern chipmunk. In the ground squirrel, both NAT activity and melatonin levels exhibited a marked nocturnal rise; these increases were not prevented by the exposure of these animals to a light irradiance of 200 microW/cm2 throughout the night. In the Eastern chipmunk, darkness at night was also associated with a marked rise in both the activity of the acetylating enzyme as well as the levels of melatonin. Again, these rhythms were not suppressed by the exposure of these animals to a light irradiance of 200 microW/cm2 for either 1 night or for 7 nights; exposure of chipmunks to light for 7 consecutive days did, however, reduce the rise in melatonin normally associated with darkness. The non-suppressibility of pineal NAT and melatonin by a 200 microW/cm2 light irradiance may relate either to the activity pattern of these animals, i.e., diurnal, or to their previous lighting history.
D000123:Acetyltransferases / Q000378:metabolism*; D000204:Activity Cycles; D000818:Animals; D002940:Circadian Rhythm; D005260:Female; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D010870:Pineal Gland / Q000201:enzymology / Q000378:metabolism*; D012377:Rodentia / Q000378:metabolism*
D000123:Acetyltransferases; D008550:Melatonin