Harderian Gland: Influence on Pineal Hydroxyindole-O-Methyltransferase Activity in Neonatal Rats

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Science  09 Oct 1970:
Vol. 170, Issue 3954, pp. 194-196
DOI: 10.1126/science.170.3954.194


A circadian rhythm has been found in hydroxyindole-O-methyltransferase activity of the pineal gland of blinded 12-day-old rats. Five additional hours of lighting can partly prevent the nocturnal increase in pineal hydroxyindole-O-methyltransferase activity in such rats. Removal of the Harderian gland abolishes this response to light in 12-day-old blinded animals, giving further support to the suggestion that this gland may function as an extraretinal photosensitive organ influencing the pineal gland in blinded suckling rats.