Yellon S M, Thorn K J, Buchanan K L, Kirby M A
Department of Physiology, Loma Linda University School of Medicine, CA 92350.
Brain Res Bull. 1993;32(1):29-33. doi: 10.1016/0361-9230(93)90315-3.
Retinal projections to the suprachiasmatic nucleus (SCN) mediate the effect of photoperiod to entrain circadian rhythms and to control reproductive maturation in the Djungarian hamster. To determine whether the retinal innervation of the SCN had fully developed by the onset of puberty in this hamster species, prepubertal and postpubertal hamsters received an intraocular unilateral injection of horseradish peroxidase (HRP), and after 24 h, the anterograde transport of HRP to the SCN was studied. In prepubertal hamsters, the retinohypothalamic tract (RHT) was found to project to the medial and caudal SCN, principally the ventrolateral regions and, to an extent, the dorsomedial portion of the nucleus. RHT innervation was asymmetric; the SCN contralateral to the monocular injection received the dominant projection. A similar pattern of retinal projections was found postpubertally; however, the ipsilateral SCN was less extensively labelled with HRP and smaller as determined by Nissl counterstain compared to that in prepubertal hamsters. These findings indicate that modifications in the retinal innervation of the SCN occur as late as puberty, and may be part of a developmental change in the mechanism which processes photoperiodic information during sexual maturation.
视网膜向视交叉上核（SCN）的投射介导了光周期对昼夜节律的调节作用，并控制了黑线仓鼠的生殖成熟。为了确定在这种仓鼠物种中，视交叉上核的视网膜神经支配在青春期开始时是否已经完全发育，对青春期前和青春期后的仓鼠进行了眼内单侧注射辣根过氧化物酶（HRP），并在24小时后，研究了HRP向视交叉上核的顺行运输。在青春期前的仓鼠中，发现视网膜下丘脑束（RHT）投射到视交叉上核的内侧和尾部，主要是腹外侧区域，并在一定程度上投射到该核的背内侧部分。RHT的神经支配是不对称的；与单眼注射对侧的视交叉上核接受主要投射。在青春期后也发现了类似的视网膜投射模式；然而，与青春期前的仓鼠相比，同侧视交叉上核用HRP标记的范围较小，并且根据尼氏复染法测定其体积也较小。这些发现表明，视交叉上核的视网膜神经支配的改变一直持续到青春期，并且可能是性成熟过程中处理光周期信息机制发育变化的一部分。
