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

Russel J. Reiter, Jack H. Britt, Jeffrey D. Armstrong

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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.

Original languageEnglish (US)
Pages (from-to)171-176
Number of pages6
JournalNeuroscience Letters
Issue number1-2
Publication statusPublished - Oct 16 1987



  • Melatonin
  • N-Acetyltransferase
  • Norepinephrine
  • Pig
  • Pineal gland

ASJC Scopus subject areas

  • Neuroscience(all)

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