The projection of GABAergic neurons of the medial terminal accessory optic nucleus to the pretectum in the rat

Large numbers of neurons were retrogradely labeled in both the dorsal and ventral medial terminal nucleous (MTN) after fluoro-gold injections into the rat pretectal nucleus of the optic tract/dorsal terminal nucleus (NOT/DTN). Fluorescence immunocytochemistry for GABA in the same brains revealed GABA-positive neurons distributed mainly in the dorsal MTN. Approximately half of all the GABAergic neurons in the MTN were double-labeled. Therefore, GABAergic neurons comprise a significant component of the MTN-NOT-DTN projection which most likely inhibits the pretectal pathway mediating horizontal optokinetic nystagmus

The development of the retinal projection to the olivary pretectal nucleus in normal and monocularly enucleated hamsters

The projection to the olivary pretectal nucleus (OPN) from the contralateral eyes is observed on the first day after birth and appears adult-like on postnatal day 5. The ipsilaeral projection is present at postnatal day 4, and expands to fill the nucleous overlapping the contralateral projection, though never as dense, between days 6 and 8. Then, in normal hamsters, ipsilaterally projecting fibers retract to the ventral side of the OPN by day 10. However, the dense expanded projection in the dorsal OPN ipsilateral to the remaining eye in monocularly enucleated hamsters persists adulthood

Ganglion cell size and distribution in the retina of the two-toed sloth (Choloepus didactylus L.)

The distribution of ganglion cell densities and sizes was studied in Nissl-stained flat-mount retinae fo the two-toed sloth. The area centrailis, a weak specializtion with low ganglion cell density, is located in the temporal retina close to the center of the eye. The presence of a visual treak was nsoted. The distribution of different ganglion cell sizes was approximately equal throughout the retina. Although the retinal organization differs from that of the closely related three-toed sloth, presumed function of retinl specializations in both species is to guide limb movements by permiting visualization of the branch along which the animal is climbing

Unusual distribution of ganglion cells in the retina of the three-toed sloth (Bradypus variegatus)

1. The distribution ans size of retinal ganglion cells labelled with horseradish preoxidase (HRP) were studied in flat-mounted retinas of three-toed sloths. 2. Massive injections of HRP solution were made throughout the thalamus and midbrain in anesthetized sloths in order to retrogradely label the retinal ganglion cell population. Twenty to thirty h later the eyes were and the retinas flat-mounted and reacted with phenylenediamine-HCL and H2O2 to label ganglion cells,thus distinguishing then from other cells int he same retinal layer. 3. Ganglion cell density graually increased from about 500 cell/mm2 at the far periphery to a peak of about 1,500 cells/mm2 in an area, termed the area centralis, deep in the inferior temporal retina. The presence of a vertical visual steak was also noted. 4. The area centralis contained a higher frequency of small ganglion cells than the peripheral retina where large cells preominated. 5. /the unusual postion of the area centralis and cisual streak in the retina can be explained by the slot's unique ability to rotate its head 180- while climbing upside-dow along horizontal branches so that the head is right-side-up. If it is assumed that the branch directly above the sloth's head needs to be visualized for accurate claw placement then the branch would be imaged on the inferior temporal retina in an area corresponding to the maximum density region