Vollrath L, Welker H A
Department of Anatomy, Johannes Gutenberg-University, Mainz, Federal Republic of Germany.
Life Sci. 1988;42(22):2223-9. doi: 10.1016/0024-3205(88)90374-8.
Previous studies involving physical-immobilization stress in laboratory rats have yielded inconsistent results with respect to melatonin synthesis in the pineal gland. As melatonin formation undergoes circadian and infradian rhythms, the aim of the present study was to examine whether stress experiments exhibit day-to-day variation. Toward this end, groups of male Sprague-Dawley rats were stressed by physical immobilization on eight consecutive days, respectively, or left relatively undisturbed, and killed. The pineal gland was rapidly dissected out and serotonin N-acetyltransferase (NAT) activity and melatonin levels were measured. NAT activity was significantly depressed on experimental days 1, 3 and 5, and slightly depressed on day 7. In addition, both in control and experimental animals NAT activity exhibited statistically significant differences between experimental days. Pineal melatonin levels were less variable. On experimental days 3 and 6 immobilization led to a significant increase of pineal melatonin levels. These results show that day-to-day variation is an important factor that influences the outcome of stress experiments and represent another example that NAT activity and pineal melatonin levels do not always show corresponding changes.
以往涉及对实验大鼠施加身体束缚应激的研究，在松果体褪黑素合成方面得出了不一致的结果。由于褪黑素的形成呈现昼夜节律和亚昼夜节律，本研究的目的是检验应激实验是否存在每日变化。为此，将雄性斯普拉格-道利大鼠分组，分别连续八天施加身体束缚应激，或相对不施加干扰，然后处死。迅速取出松果体，测量血清素N-乙酰基转移酶（NAT）活性和褪黑素水平。在实验第1、3和5天，NAT活性显著降低，第7天略有降低。此外，无论是对照动物还是实验动物，NAT活性在各实验日之间均存在统计学显著差异。松果体褪黑素水平的变化较小。在实验第3和6天，束缚导致松果体褪黑素水平显著升高。这些结果表明，每日变化是影响应激实验结果的一个重要因素，也是NAT活性和松果体褪黑素水平并不总是呈现相应变化的又一个例证。
