Nucleus Geniculatus Lateralis Pars Dorsalis

Using histochemical determination of activity of the mitochondrial oxidative enzyme cytochrome oxidase (CO) in brain structures, metabolic activity both in turtles and in lizards has been shown to be higher in centers of the tectofugal channel (the tectal stratum griseum centrale, SGC; nucleus pretectalis ventralis, Ptv; thalamic nucleus rotundus, Rot; telencephalic visual area of the anterior dorsal ventricular ridge, Advr) than in the thalamofugal channel centers (the thalamic Nucleus geniculatus lateralis pars dorsalis, GLd; cortex dorsolateralis, Cxdl; and pallial thickening, Path) of the visual system.  

We found that M-L axis and A-P axis in HA were transferred into the dorsal-ventral axis and the medial-lateral axis, respectively within the Nucleus geniculatus lateralis pars dorsalis (GLd).  

Immunopositive neurons were densely distributed in the dorsal thalamus (particularly in the perirotundal belt), the area triangularis, the Nucleus geniculatus lateralis pars dorsalis, the periventricular hypothalamus and the medial eminence.  

Two ascending gamma-aminobutyric acid (GABA)ergic pathways to thalamic visual centers were revealed: a weak projection from the retinorecipient nucleus lentiformis mesencephali to the ipsilateral Nucleus geniculatus lateralis pars dorsalis and a considerably stronger projection from the nonretinorecipient nucleus pretectalis ventralis to the nucleus rotundus.  

Rhodamine B Isothiocyanate (RITC), Fluorogold (FG) and True blue (TB) were injected into either the visual Wulst (thalamofugal pathway) or the nucleus rotundus (Rt; tectofugal pathway) and the retrogradely labelled neurones in the Nucleus geniculatus lateralis pars dorsalis (GLd) or the optic tectum, respectively, were counted.  

After injecting fluorogold (FG) into one side of the visual Wulst and rhodamine B isothiocyanate (RITC) into the other side of the visual Wulst, the labeled neurons in the Nucleus geniculatus lateralis pars dorsalis (GLd) were examined.  

The retinal ganglion cells project contralaterally to thalamus (Nucleus geniculatus lateralis pars dorsalis, nucleus geniculatus lateralis pars ventralis and nucleus ventrolateralis pars ventralis and nucleus ventrolateralis pars ventralis), pretectum (nucleus lentiformis mesencephali, nucleus geniculatus pretectalis and nucleus posterodorsalis) and optic tectum (layers 14 and 12, mainly, and layers 13 and 11).  

In the 5 species the retinal ganglion cells project to the contralateral hypothalamus (nucleus suprachiasmaticus), thalamus (nucleus geniculatus lateralis pars ventralis, Nucleus geniculatus lateralis pars dorsalis), pretectum (nuclei lentiformis mesencephali, geniculatus pretectalis, postero-dorsalis griseus tectalis), tectum opticum (layer 2 to layer 6 of the stratum griseum et fibrosum superficiale) and tegmentum mesencephali (nucleus opticus tegmenti). Ipsilateral optic fibers were never observed in Uromastix acanthinurus, whereas an uncrossed quota was visible in both Nucleus geniculatus lateralis pars dorsalis and nucleus postero-dorsalis in the other species.  

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