Vollrath L, Huesgen A
Department of Anatomy, Johannes Gutenberg University, Mainz, Federal Republic of Germany.
J Neural Transm. 1988;72(1):55-66. doi: 10.1007/BF01244632.
Serotonin N-acetyltransferase (NAT), which is crucial for the formation of melatonin, undergoes a typical day/night rhythm in the pineal gland with low levels during daytime and high levels at night. Short pulses of light given at night have been shown to rapidly depress NAT activity in some species, but not in others, the reasons for this difference being unclear. As diurnality and nocturnality of the experimental animals may play a role and since diurnally active animals have been little investigated in this respect, in the present study the diurnally active guinea pig was investigated. Male guinea pigs kept under a lighting regimen of LD 12:12 (lights off at 1700 hrs) were killed between 1200 or 1300 hrs and between 0000 and 0200 hrs, at night in the dark or after exposure to 10 or 45 min of light. The results obtained show that the day/night difference of NAT activity is about 2-fold. 10 min or 45 min of light given at night significantly depress pineal NAT activity. Re-exposure to darkness for 1 hr of animals previously given light for 10 min leads to restoration of NAT activity. These findings together with data from the literature suggest that it does not appear to be the activity pattern (diurnality versus nocturnality) of an animal nor the amplitude of the day/night difference of pineal NAT activity that account for the suppressibility or non-suppressibility of pineal NAT activity by light at night.
血清素N - 乙酰基转移酶（NAT）对褪黑素的形成至关重要，它在松果体中呈现典型的昼夜节律，白天水平低，夜间水平高。夜间给予的短时光脉冲已被证明在某些物种中会迅速降低NAT活性，但在其他物种中则不会，这种差异的原因尚不清楚。由于实验动物的昼行性和夜行性可能起作用，并且鉴于昼行性活动的动物在这方面研究较少，在本研究中对昼行性活动的豚鼠进行了研究。将雄性豚鼠置于LD 12:12（1700时熄灯）的光照方案下，分别在1200或1300时以及0000至0200时处死，夜间在黑暗中或在暴露于10或45分钟光照后处死。获得的结果表明，NAT活性的昼夜差异约为2倍。夜间给予10分钟或45分钟的光照会显著降低松果体NAT活性。先前给予10分钟光照的动物重新暴露于黑暗1小时会导致NAT活性恢复。这些发现与文献数据一起表明，似乎不是动物的活动模式（昼行性与夜行性），也不是松果体NAT活性的昼夜差异幅度决定了夜间光照对松果体NAT活性的抑制或非抑制作用。
