Melatonin implants disrupt developmental synchrony regulated by flexible interval timers.
Melatonin implants disrupt developmental synchrony regulated by flexible interval timers.
复制标题
褪黑激素植入物会破坏由灵活的间隔计时器调节的发育同步性。
DOI：
10.1046/j.1365-2826.2003.01104.x
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发表时间：
2003
影响因子：
3.2
通讯作者：
Gorman,MR
中科院分区：
文献类型：
--
作者：
Gorman,MR
在繁殖季节结束时出生的西伯利亚仓鼠从出生起就受到生殖抑制，性腺成熟延迟到第二年春天。这种春季向生殖表型的转变与体重的突然增加相一致，这两个过程都是由一种间隔计时机制触发的，这种机制对短日照抑制变得不敏感或难以控制。先前已经证明，出生于模拟自然光周期的仓鼠在8月初比出生于9月光周期的仓鼠在更晚的年龄成为光不应性。由于间隔计时器编程的持续时间具有灵活性，季节性出生队列的发育与实验室光周期模拟的日历日期同步。在本研究中，仓鼠出生在模拟8月或9月的光周期。来自每个队列的仓鼠被给予可移除的恒定释放褪黑激素植入物，以可逆地模糊3至9周龄或9-15周龄之间的日照长度的神经内分泌表现。 当对照仓鼠在整个过程中给予蜂蜡胶囊时，8月出生的雄性在光不应性发作时比9月出生的雄性大约6周，这通过体重和睾丸大小的加速增加来评估。 雌性动物的体重模式相同。这些措施在日历日期方面是同步的。从3-9周龄开始，褪黑激素胶囊破坏了队列的同步，但随后的植入物没有破坏。 褪黑激素植入物通过影响9月出生的仓鼠的发育轨迹而不影响8月队列来改变同步。这些结果表明，光不应性的间隔计时器的功能受到光周期和褪黑激素的影响。褪黑激素信号的内源性模式调节由间隔计时器测量的持续时间，以确保季节性群组的发育里程碑与环境条件同步。
Siberian hamsters born into short daylengths near the end of the breeding season are reproductively inhibited from birth and delay gonadal maturation until the following spring. This vernal transition to a reproductive phenotype coincides with an abrupt increase in body weight, and both processes are triggered by an interval timing mechanism that becomes insensitive, or refractory, to short‐day inhibition. It was previously demonstrated that hamsters born into simulated natural photoperiods in early August became photorefractory at later ages than hamsters born into September photoperiods. As a consequence of flexibility in the duration programmed by the interval timer, development of seasonal birth cohorts was synchronous with respect to the calendar date simulated by laboratory photoperiod. In the present study, hamsters were born into simulated August or September photoperiods. Hamsters from each cohort were given removable constant release melatonin implants to reversibly obscure the neuroendocrine representation of daylength between 3 and 9 weeks or 9–15 weeks of age. When control hamsters were given beeswax capsules throughout, August‐born males were approximately 6 weeks older than September males at the onset of photorefractoriness as assessed by accelerated increases in body weight and testicular size. Females exhibited the same pattern in body weight. These measures were synchronized with respect to calendar date. Synchronization of cohorts was disrupted by melatonin capsules from 3–9 weeks of age but not by later implants. Melatonin implants altered synchronization by influencing the developmental trajectory of September‐born hamsters without influencing the August cohort. These results demonstrate that the function of the interval timer underlying photorefractoriness is influenced by photoperiod and by melatonin. The endogenous pattern of melatonin signals adjusts the duration measured by the interval timer to insure that developmental milestones of seasonal cohorts are synchronized with environmental conditions.