Circadian Rhythm of Serotonin <i>N</i> -Acetyltransferase Activity in Organ Culture of Chicken Pineal Gland

Abstract

When chicken pineal glands were organ-cultured in darkness, serotonin N-acetyltransferase activity was low during daytime, increased at midnight, and decreased on the next morning. The autonomous increase of N-acetyltransferase activity was suppressed by illumination of the glands. When pineal glands were cultured under a light-dark cycle (LD 12:12), the change of N-acetyltransferase activity continued to oscillate in phase with the light-dark cycle for 3 days.