Institute for cellular and integrative neuroscience (INCI), Department Neurobiology of Rhythms, University of Strasbourg, Strasbourg, France.
J Biol Rhythms. 2013 Aug;28(4):278-90. doi: 10.1177/0748730413498561.
In mammals, the pineal hormone melatonin is thought to be essential to process environmental photoperiodic information. In this study, we demonstrate in a circannual species, the European hamster Cricetus cricetus, the existence of a melatonin-independent second pathway. In 4 physiological parameters (reproduction, body weight, activity pattern, body temperature), a large majority of pinealectomized European hamsters were entrained to an accelerated photoperiodic regime. It compressed the natural variations in the photoperiod to a 6-month cycle, which allowed us to record up to 6 complete physiological cycles during the life span of the individuals. We show further that whether a pinealectomized animal is able to entrain to changes in the photoperiod is influenced by the season of pinealectomy. The results do not disprove that melatonin is capable of entraining a circannual rhythm, but they show clearly that melatonin is not necessary, demonstrating another melatonin-independent pathway for circannual entrainment by the photoperiod. In view of these new insights, a revision of the original literature revealed that probably the melatonin-independent pathway plays an important role in most circannual mammals but only a minor role in photoperiodic species. Thus, the present work provides also the first evidence for different synchronization mechanisms in photoperiodic and circannual species.
在哺乳动物中，松果体激素褪黑素被认为是处理环境光周期信息所必需的。在这项研究中，我们在一个年周期物种，即欧洲仓鼠（Cricetus cricetus）中证明了存在褪黑素独立的第二条途径。在 4 个生理参数（繁殖、体重、活动模式、体温）中，大多数松果体切除的欧洲仓鼠被加速光周期方案所驯化。它将自然光周期的自然变化压缩到 6 个月的周期内，这使我们能够在个体的寿命内记录多达 6 个完整的生理周期。我们进一步表明，松果体切除动物是否能够适应光周期的变化，受到松果体切除术季节的影响。结果并不能否定褪黑素能够驯化年周期节律，但它们清楚地表明，褪黑素不是必需的，证明了光周期驯化年周期的另一条褪黑素独立途径。鉴于这些新的见解，对原始文献的修订表明，可能褪黑素独立途径在大多数年周期哺乳动物中起着重要作用，但在光周期物种中只起次要作用。因此，本工作还首次为光周期和年周期物种的不同同步机制提供了证据。
