PROCESSING OF PHOTIC INFORMATION WITHIN THE INTERGENICULATE LEAFLET OF THE LATERAL GENICULATE-BODY - ASSESSED BY NEUROPEPTIDE-Y IMMUNOREACTIVITY IN THE SUPRACHIASMATIC NUCLEUS OF RATS
PROCESSING OF PHOTIC INFORMATION WITHIN THE INTERGENICULATE LEAFLET OF THE LATERAL GENICULATE-BODY - ASSESSED BY NEUROPEPTIDE-Y IMMUNOREACTIVITY IN THE SUPRACHIASMATIC NUCLEUS OF RATS
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DOI：
10.1016/0306-4522(93)90129-4
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发表时间：
1993-10-01
期刊：
影响因子：
3.3
通讯作者：
INOUYE, SIT
中科院分区：
文献类型：
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作者：
SHINOHARA, K;TOMINAGA, K;INOUYE, SIT
视交叉上核的昼夜节律起搏器是通过视网膜下丘脑束和下丘脑束这两条神经通路来完成的。下丘脑膝间束起源于膝间小叶和膝外侧腹侧核的一部分，由对神经肽Y具有免疫反应的纤维组成。为了评价下丘脑膝间束对光信息的加工，采用微孔组织酶免疫法测定了不同外界光照条件下大鼠视交叉上核的神经肽Y免疫反应性。连续光照下大鼠视交叉上核神经肽Y水平稳定升高，并在2 h内达到峰值，然后恢复到基础水平。增加的数量不取决于光照射的强度和持续时间。短至5分钟的光脉冲引起神经肽Y的类似上升，表明这种反应是由于从黑暗到光明的突然转变。然而，这种反应仅在起搏器的昼夜节律时间0（主观黎明）发生从暗到光的转变时观察到。昼夜节律时间0的光脉冲可以有效地诱导神经肽Y水平的增加，但不会显著改变昼夜节律的相位。这一观察结果表明，利用神经肽Y的光通路可能只有在内源性昼夜节律与外部光暗周期同步时才起作用。兴奋性氨基酸拮抗剂（MK-801）阻断了光对神经肽Y的增加，而激动剂（n -甲基- d -天冬氨酸）对大鼠视交叉上核神经肽Y水平的促进作用与光相似。这些结果表明，下丘脑束处理光信息，以促进在主观黎明或黄昏时发生的光与暗之间的转换的区分。
Entrainment of the circadian pacemaker in the suprachiasmatic nucleus is accomplished by two neural pathways, the retinohypothalamic and geniculohypothalamic tracts. The geniculohypothalamic tract, which originates from the intergeniculate leaflet and a portion of the ventral lateral geniculate nucleus, is composed of fibers immunoreactive to neuropeptide Y. To assess the processing of photic information by the geniculohypothalamic tract, neuropeptide Y immunoreactivity in the suprachiasmatic nucleus of rats kept under various external lighting conditions was determined by enzyme immunoassay of micropunched tissues.Neuropeptide Y levels in the suprachiasmatic nucleus steadily increased when rats were exposed to continuous light and reached a peak in 2 h before returning to basal level. The amount of increase did not depend on intensity and duration of light exposure. A light pulse as short as 5 min elicited a similar rise in neuropeptide Y, indicating that the response is due to the sudden transition from dark to light. This response, however, was only observed when the dark to light transition occurred at circadian time 0 (subjective dawn) of the pacemaker. A light pulse at circadian time 0, which effectively induces the increase in neuropeptide Y level, does not significantly shift the phase of the circadian rhythm. This observation indicates that the photic pathway utilizing neuropeptide Y may be functional only when the endogenous circadian rhythm is synchronized to external light and dark cycles. Administration of an excitatory amino acid antagonist (MK-801) blocked the increase of neuropeptide Y by light, while an agonist (N-methyl-D-aspartate) induced similar facilitatory effects to that of light on the neuropeptide Y level in the rat suprachiasmatic nucleus.These results suggest that the geniculohypothalamic tract processes photic information so as to facilitate distinction of the transition between light and darkness that occurs either at subjective dawn or dusk.