Title

Absence of a nocturnal rise in either norepinephrine, N-acetyltransferase, hydroxyindole-O-methyltransferase or melatonin in the pineal gland of the domestic pig kept under natural environment photoperiods

Author Info

Russel J. Reiter, University of Texas Health Science - San Antonio
Jack H. Britt, North Carolina State University at Raleigh
Jeffrey D. Armstrong, North Carolina State University at Raleigh

Recommended Citation

Postprint version. Published in Neuroscience Letters, Volume 81, Issue 1-2, October 1, 1987, pages 171-176.

Copyright © 1987 Elsevier.

NOTE: At the time of publication, the author Jeffrey D. Armstrong was not yet affiliated with Cal Poly.

The definitive version is available at https://doi.org/10.1016/0304-3940(87)90360-0.

Abstract

Castrated male and intact female pigs were kept under natural photoperiodic and temperature conditions and were killed over a 24 h period in either May (under long days) or in December (under short days). Neither the pineal norepinephrine (NE) concentration nor the melatonin content rose at night; likewise, neither the activities of N-acetyltransferase (NAT) nor hydroxyindole-O-methyltransferase (HIOMT) increased during darkness. In May pineal melatonin content actually decreased (P < 0.05) at night while in December NAT activity fell (P < 0.05) at night. Daytime levels of each of these variables were equivalent to those measured in other species. The absence of a nocturnal increase in pineal melatonin production in either May or December raises the possibility that pineal melatonin may be involved in regulating seasonal breeding in the pig in a manner different from other mammals. Alternatively, pineal melatonin production may be unrelated to seasonal reproduction in the pig.