DIURNAL FLUCTUATION IN THE ENZYME-ACTIVITY AND THE MESSENGER-RNA LEVEL OF PINEAL SEROTONIN N-ACETYLTRANSFERASE IN NORMAL AND HEREDITARY MICROPHTHALMIC RATS

The enzyme activity and the messenger RNA level of pineal serotonin N- acetyltransferase were more than 20- and 50-fold higher, respectively, in the dark period than in the light period in normal rats. In heredi tary microphthalmic rats, however, the serotonin N-acetyltransferase a ctivity and its mRNA level did not undergo a great diurnal change thro ugh the light and dark periods. These results indicate that the diurna l rhythms of the activity and the mRNA level of serotonin N-acetyltran sferase are not detected in the pineal gland of hereditary blind rats, suggesting free-running rhythms in individual animals due to desynchr onization of their circadian rhythms by a lack of their optic nerve.