The Intergeniculate Leaflet Partially Mediates Effects of Light on Circadian Rhythms

摘要: Photic signals affect circadian activity rhythms by both phasic and tonic mechanisms that modulate pacemaker phase period. In mammals, the effects of light on are mediated retina, which communicates with suprahiasmatic nucleus (SCN) two different anatomical routes: retino-hypothalamic tract (RHT), originating in geniculo-hypothalamic (GHT), arising from a retino-recipient nucleus, intergeniculate leaflet (IGL). We assessed roles these afferent systems mediating IGL-lesioned animals. Destruction IGL significantly affected shifts produced brief pulses (phasic effect) modified change period (tau) free-running rhythm changing level constant (LL) (tonic effect). Phase advances were decreased amplitude while delays increased animals as compared to controls. The dark (tau DD) was greater than tau DD controls, lengthening normally LL not observed or greatly reduced Entrainment light-dark cycles unaffected lesions, other aspects response (e.g., activity-rest ratio, total activity, splitting). Our data support interpretation plays significant role relaying information regarding illumination intensity SCN.