Alamilla Javier, Granados-Fuentes Daniel, Aguilar-Roblero Raúl
CONACYT Research Fellow - Centro de Investigaciones Biomédicas de la Universidad de Colima, Colima, México.
Department of Biology, Washington University, St Louis, MO, USA.
Eur J Neurosci. 2015 Nov;42(10):2833-42. doi: 10.1111/ejn.13088. Epub 2015 Nov 2.
The suprachiasmatic nucleus (SCN) in mammals is the master clock which regulates circadian rhythms. Neural activity of SCN neurons is synchronized to external light through the retinohypothalamic tract (RHT). The paraventricular thalamic nucleus (PVT) is a neural structure that receives synaptic inputs from, and projects back to, the SCN. Lesioning the anterior PVT (aPVT) modifies the behavioral phase response curve induced by short pulses of bright light. In order to study the influence of the aPVT on SCN neural activity, we addressed whether the stimulation of the aPVT can modulate the electrical response of the SCN to either retinal or RHT stimulation. Using in vitro and in vivo recordings, we found a large population of SCN neurons responsive to the stimulation of either aPVT or RHT pathways. Furthermore, we found that simultaneous stimulation of the aPVT and the RHT increased neuronal responsiveness and spontaneous firing rate (SFR) in neurons with a low basal SFR (which also have more negative membrane potentials), such as quiescent and arrhythmic neurons, but no change was observed in neurons with rhythmic firing patterns and more depolarized membrane potentials. These results suggest that inputs from the aPVT could shift the membrane potential of an SCN neuron to values closer to its firing threshold and thus contribute to integration of the response of the circadian clock to light.
哺乳动物的视交叉上核（SCN）是调节昼夜节律的主时钟。SCN神经元的神经活动通过视网膜下丘脑束（RHT）与外部光线同步。丘脑室旁核（PVT）是一种神经结构，它接收来自SCN的突触输入并投射回SCN。损毁前PVT（aPVT）会改变由短脉冲强光诱导的行为相位反应曲线。为了研究aPVT对SCN神经活动的影响，我们探讨了刺激aPVT是否能调节SCN对视网膜或RHT刺激的电反应。通过体外和体内记录，我们发现大量SCN神经元对aPVT或RHT通路的刺激有反应。此外，我们发现同时刺激aPVT和RHT会增加基础SFR较低（其膜电位也更负）的神经元的神经元反应性和自发放电率（SFR），如静止和无节律的神经元，但在有节律放电模式和膜电位更去极化的神经元中未观察到变化。这些结果表明，来自aPVT的输入可能会将SCN神经元的膜电位转移到更接近其放电阈值的值，从而有助于昼夜节律时钟对光反应的整合。
