Author/Editor		Križaj, David; Hawlina, Marko
Title		Cellular basis rod-cone interactions in the outer retina
Translated title		Celična podlaga medsebojnega vpliva med paličnicami in čepnicami v zunanjih plasteh mrežnice
Type		članek
Source		Zdrav Vestn
Vol. and No.		Letnik 71, št. Suppl 2
Publication year		2002
Volume		str. II-137-45
Language		eng
Abstract		Background. At least twice daily our retinas move between a light adapted, cone-dominated (photopic) state and a dark-adapted, color-blind and highly light-sensitive roddominated (scotopic) state. In between is a rather ill-defined transitional state called the mesopic state in which retinal circuits express both rod and cone signals. Consequently, in the mesopic state the retinal output to the brain contained in the firing patterns of the ganglion cells consists of information derived from both rod and cone signals. Morphology, physiology and psychophysics all contributed to an understanding that the two systems are not independent but interact extensively via both pooling and mutual inhibition. This review lays down a rationale for such rod-cone interactions in the vertebrate retinas. It suggests that the important functional roles of rod-cone interactions is in that they shorten the duration of the mesopic state. As a result, the retina is maintained in either in the (rod-dominated) high sensitivity photon counting mode or in the second mode which emphasizes temporal transients and spatial resolution (the cone-dominated photopic state). Conclusions. Experimental evidence for pre- and postsynaptic mixing of rod and cone signals in the retina is shown together with the preeminent neuromodulatory role of both light and dopamine in controling inter-actions between rod and cone signals. Dopamine is shown to be both necessary and sufficient to mediate light adaptation in the retina.
Summary		Izhodišča. Vsaj dvakrat na dan se naše mrežnice prilagajajo osvetlitvi in s tem spreminjajo stanje, pri katerem prevladujejo čepnice (cone-dominated), v tistega, kjer prevladujejo paličnice (rod dominated). Med tema stanjema je prehodno obdobje, ki je nekoliko ohlapno označeno kot mezopično stanje. V tem stanju se v mrežnici prepletajo tako signali paličnic in čepkov. Posledično se v mezopičnem stanju v električnem odvodu ganglijskih celic mrežnice nahajajo tako vzorci aktivacije ganglijskih celic po vzdraženju paličnic kot tudi čepnic. Morfologija, fiziologija in psihofizične metode vse prispevajo k razumevanju tega, da oba sistema nista neodvisna, ampak sodelujeta tako preko sočasnih spodbujevalnih kot tudi zaviralnih mehanizmov. Ta pregled prinaša oris soodvisnega delovanja paličnic in čepnic v mrežnicah vretenčarjev in predstavlja tezo, da je pomen interakcije med paličnicami in čepnicami v skrajšanju trajanja mezopičnega stanja na najmanjšo možno mero. Zaključki. Predstavljeni so mehanizmi pred- in posinaptične regulacije signalov paličnic in čepnic in poudarjena nevromodulatorna vloga svetlobe, dopamina ter ostalih nevromodulatorjev v mrežnici pri regulaciji stanja adaptacije in metabolizmu retinalnega pigmentnega epitelija in posameznih vrst celic. Rezultati kažejo, da je dopamin nepogrešljiv in zadosten mediator svetlobne adaptacije v mrežnici.
Descriptors		PHOTORECEPTORS DOPAMINE RODS (RETINA) CONES (RETINA) ADAPTATION, OCULAR ELECTRORETINOGRAPHY