Spatial relationships of axons arising from the substantia nigra, spinal trigeminal nucleus, and pedunculopontine tegmental nucleus within the intermediate gray of the cat superior colliculus

Abstract

We have utilized two different anterograde transport methods (Phaseolus vulgaris leucoagglutinin [PHA-L] immunocytochemistry and autoradiography) in the same experiment to compare the sublaminar location and arrangement of tectopetal axons arising from the substantia nigra pars reticulata, the spinal trigeminal nucleus, and the pedunculopontine tegmental nucleus. Our findings reveal that the nigrotectal projection terminates in a patchy fashion within three horizontally oriented sublaminae of the stratum griseum superficiale (SGI), the dorsal, middle and ventral. The middle tier of nigrotectal axons exhibits an exquisite, puzzle-like, complementary spatial relationship with trigeminotectal axons. In contrast, axons arising from the pedunculopontine tegmental nucleus overlap with patches of nigrotectal axons within the middle tier. Thus the middle tier of the SGI consists of domains of overlapping nigral and pedunculopontine tegmental inputs which interdigitate with domains rich in somatosensory inputs.

Honeycomb-like structure of the intermediate layers of the rat superior colliculus, with additional observations in several other mammals: AChE patterning

“…This observation was later confirmed by retrograde labeling of different classes of efferent collicular neurons (Castiglioni et al, 1978;Huerta et al, 1981;Murray and Coulter, 1982;Yamasaki et al, 1986). In parallel, there is a patchy innervation of most, if not all, of the collicular afferents (from cortex, Goldman and Nauta, 1976;Kü nzle and Akert, 1977;Leichnetz et al, 1981;Segal et al, 1983;Clemo and Stein, 1983; from subcortical sensory relays, Kudo and Niimi, 1980;Tashiro et al, 1980;Huerta et al, 1981;Kudo, 1981;Huerta and Harting, 1982;Harting and Van Lieshout, 1991; from basal ganglia, Jayaraman et al, 1977;Graybiel, 1978a;Beckstead et al, 1979;Harting and Van Lieshout, 1991;Redgrave et al, 1992; from cerebellum, Kawamura et al, 1982; from hypothalamus, Rieck et al, 1986). Patches in the intermediate layers are regularly described in the frontal plane as a series of groups of either terminals or neurons with generally increased size from medial to lateral SC.…”

Reversible visual hemineglect.

“…The direct pathways terminate at the interface between the superficial and deep portions of the SC (21), where the cortically derived signals directly activate motor output neurons that evoke orienting responses of eyes and head (22). The indirect pathways involve multiple sign-inverting circuits that include the caudate, putamen, and substantia nigra and lead to SGS, SO, and SGI (23)(24)(25)(26). However, it is important to recognize that the exact nature of the influences mediated by the indirect pathway on motor systems is poorly understood, although important links between substantia nigra and head and eye movements have been made in cats (27)(28)(29), as they have been in monkeys (30,31).…”

Inhibition of Nitric Oxide Synthase Fails to Disrupt the Development of Cholinergic Fiber Patches in the Rat Superior Colliculus

“…These cell clusters precisely overlap fiber patches in the IGL that arise from mesencephalic tegmen tal nuclei and that contain ACh [19,20]. Fibers from the substantia nigra that contain GABA [21], and those from the prefrontal eye fields that probably contain glutamate, also form patches that overlap those containing ACh [22,23]. The patch-cluster system is not as well defined in the rat, but fiber patches in the rat SC also arise from brain stem nuclei and contain ACh [20].…”