Day-Night Differences in the Response of the Pineal Gland to Swimming Stress

Wutian Wu, Yi Ci Chen, Russel J. Reiter

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The effect of swimming stress on pineal N-acetyltransferase activity, hydroxyindole-O-methyltransferase (HIOMT) activity, and melatonin content was studied during the day and night in adult male rats. At night, elevated pineal activity was suppressed by light exposure before the animals swam. During the day, swimming for 2 hr did not stimulate NAT activity unless the animals were pretreated with desmethylimipramine (DMI), a norepinephrine uptake blocker. Pineal melatonin content after daytime swimming exhibited a weak rise, unless DMI was injected, in which case melatonin levels showed a highly significant increase. Swimming at night caused a greater (compared to daytime levels) increase in NAT activity in both noninjected and DMI-injected rats. Melatonin levels at night were highly significantly stimulated (compared to daytime values) even without pretreatment of the rats with DMI. The greater response of the rat pineal to swimming stress at night may relate either to an increase in the number of β-adrenergic receptors in the pinealocyte membrane at night or to a reduced capacity of the sympathetic neurons in the pineal to take up excess circulating catecholamines. Pineal HIOMT activity was not influenced by swimming (with or without DMI) either during the day or at night.

Original languageEnglish (US)
Pages (from-to)315-319
Number of pages5
JournalProceedings of the Society for Experimental Biology and Medicine
Issue number3
StatePublished - Mar 1988

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology


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