The retinal projection to the cat pretectum

Abstract

Retinal ganglion cells were labeled retrogradely by localized injections of HRP into different regions of the pretectum, tectum, and optic tract in 26 cats. Retinal projection zones in the pretectum were labeled anterogradely in the same cats by intravitreal injections of 3H-proline. This allowed the HRP injection sites to be located with respect to the retinal termination zones. The form of the projection zones from retina to pretectum was determined from serial reconstructions of either coronal or horizontal sections. The zones are best distinguished in horizontal sections, where they are seen as four roughly parallel strips on either side of the brain. They are more-or-less parallel to the anterior border of the tectum, and appear to traverse the entire width of the retinal projection to the tectum. Each zone is similar in form for the ipsilateral and contralateral projections, although the contralateral projection is thicker and denser. Binocular injections of 3H-proline showed that the projections from the two eyes were in register and did not interdigitate. Cells labeled by HRP injections in the anteromedial end of the pretectum were concentrated in the lower nasal quadrant of the contralateral retina, and the lower temporal quadrant of the ipsilateral retina. Posterolateral injections labeled cells in the upper quadrants. There is thus a rough retinotopic mapping along the elongated axis of the pretectum. When the distributions of ganglion cells labeled by HRP injections to different parts of the pretectum are combined, they show a concentration in both the visual streak and area centralis, and thereby reflect, at least qualitatively, the relative spatial distribution of the entire ganglion-cell population. About 85% of the retinal projection to the pretectum is contralateral. For all of the HRP injections, the spatial density of labeled cells was always low, accounting for no more than 3% of the total spatial density of ganglion cells in any retinal region. Several types of ganglion cells were labeled following injections to most regions of the pretectum; these included alpha, beta, and epsilon cells, as well as small-bodied cells showing a variety of morphologic forms. Alpha cells were labeled mainly from the anterolateral end of the pretectum, but other cell types were labeled from all injected regions. In the peripheral retina, 2% of the labeled cells were alpha cells, 32% were beta cells, 19% were epsilon cells, and the remaining 47% were small cells whose dendrites only occasionally filled to any significant extent.(ABSTRACT TRUNCATED AT 400 WORDS)

Retinal ganglion cell projections to the hamster suprachiasmatic nucleus, intergeniculate leaflet, and visual midbrain: Bifurcation and melanopsin immunoreactivity

“…A previous report in the hamster found the ganglion cells projecting to the OPT to be located in a somewhat more widespread inferior-temporal quadrant (Young and Lund, 1998). It has been suggested that there is retinotopic mapping of projections to the cat pretectum (Koontz et al, 1985). Retinotopographic mapping could account for within-and between-study differences in reported ganglion cell distributions.…”

Cytoarchitectonic and connectional organization of the ventral lateral geniculate nucleus in the cat

“…Projections to the LGv from the SC reportedly arise from both superficial and intermediate layers (Graham, 1977), and autoradiographic studies showed the LGv to project to the deep part of layers 2 and 4 of the SC (Edwards et al, 1974;Swanson et al, 1974). The Y-type retinal ganglion cells project to the deep part of layer 2 (McIlwain and Lufkin, 1976;Itoh et al, 1981) and to the nucleus of the optic tract of the pretectum (Ballas and Hoffmann, 1985;Koontz et al, 1985;Leventhal et al, 1985). The Y-cells also project to LGv (Mize and Horner, 1984) and, because of the existence of the projection from IL to the superficial layers of SC, Y-cell projections probably terminate in IL.…”

“…The retinal projections to L probably arise from W-type ganglion cells, because W-cells project to the superficial part of layer 2 of SC and the pretectum Mize and Horner, 1984;Koontz et al, 1985;Leventhal et al, 1985), both of which have connections with L. Retinal W-cells were also reported to project to the lamina C1 and C2 of the dorsal lateral geniculate nucleus (Wilson and Stone, 1975). Similarly, cells in the superficial part of layer 2 of the SC project to layers C1 and C2 of the lateral geniculate nucleus , and are supposed to comprise part of the W system.…”

“…The retinal projections to M were supposed to arise from W-cells, as the retinal W-cells project to the superficial part of layer 2 of the SC, the LGv, and the pretectum (McIlwain, 1978;Itoh et al, 1981;Mize and Horner, 1984;Ballas and Hoffmann, 1985;Koontz et al, 1985;Leventhal et al, 1985;Chen et al, 1996), all of which are interconnected. In rodents, light-sensitive, melanopsin-positive ganglion cells project to the above regions, and some of them project to both the suprachiasmatic nucleus and the intergeniculate leaflet (Gooley et al, 2001;Berson et al, 2002;Hannibal et al, 2002;Hattar et al, 2002;Morin et al, 2003).…”

The thalamus as a monitor of motor outputs

“…On the basis of retrograde transport experiments, Wässle & Illing (1980) reported that 10% of these cells project to the superior colliculus. Koontz et al (1985) reported that X cells could be retrogradely labelled by injections into the pretectum, whereas Leventhal et al (1985) found no X cell axons going to the superior colliculus and only ca. 1% going to the pretectum.…”