Superior colliculus projections to midline and intralaminar thalamic nuclei of the rat

Abstract

The superior colliculus (SC) projections to the midline and intralaminar thalamic nuclei were examined in the rat. The retrograde tracer cholera toxin beta (CTb) was injected into one of the midline thalamic nuclei-paraventricular, intermediodorsal, rhomboid, reuniens, submedius, mediodorsal, paratenial, anteroventral, caudal ventromedial, or parvicellular part of the ventral posteriomedial nucleus-or into one of the intralaminar thalamic nuclei-medial parafascicular, lateral parafascicular, central medial, paracentral, oval paracentral, or central lateral nucleus. After 10-14 days, the brains from these animals were processed histochemically, and the retrogradely labeled neurons in the SC were mapped. The lateral sector of the intermediate gray and white layers of the SC send axonal projections to the medial and lateral parafascicular, central lateral, paracentral, central medial, rhomboid, reuniens, and submedius nuclei. The medial sector of the intermediate and deep SC layers project to the parafascicular and central lateral thalamic nuclei. The paraventricular thalamic nucleus is innervated almost exclusively by the medial sectors of the deep SC layers. The superficial gray and optic layers of the SC do not project to any of these thalamic areas. The discussion focuses on the role these SC-thalamic inputs may have on forebrain circuits controlling orienting and defense (i.e., fight-or-flight) reactions.

Limbic thalamus and state-dependent behavior: The paraventricular nucleus of the thalamic midline as a node in circadian timing and sleep/wake-regulatory networks

“…periaqueductal gray (Krout and Loewy, 2000a,b;Krout et al, 2002;Li and Kirouac, 2012). A limited input deriving from the deep layers of the superior colliculus was also reported (Krout et al, 2001). In the rat, contingents of cortical and subcortical fibers which innervate PVT send collaterals to the nucleus of the solitary tract, a feature that has been implicated in the simultaneous modulation of visceral reflex excitability and thalamocortical activity (Otake et al, 1994).…”

Topographic Organization of Excitatory and Inhibitory Commissural Connections in the Superior Colliculi and Their Functional Roles in Saccade Generation

“…In addition, a smaller number of TRNs with commissural collaterals were observed in the SP. Tectothalamic neurons are mainly located in the SGS (Bickford and Hall 1989), but some thalamic nuclei such as the paraventricular nucleus (Krout et al 2001), central lateral nucleus (Yamasaki et al 1986), and the mediodorsal nucleus (Bickford and Hall 1989;Harting et al 1980) are innervated by the deeper SC layers. Therefore TRNs with commissural collaterals might include such tectothalamic neurons.…”

Chronic Lithium Administration to Rats Selectively Modifies 5-HT2A/2C Receptor-Mediated Brain Signaling Via Arachidonic Acid

“…In 13 of the 70 regions, LiCl feeding compared with control diet had a significant main effect on k*, elevating k* to the same extent following saline or DOI injection. Of the 13 regions, layers IV and VI of the auditory cortex, and medial habenular and parafascicular nucleus are considered to participate in auditory or visual circuitry (Brodal, 1981;Krout et al, 2001). Five of the 70 regions did not have a significant main effect of either DOI or LiCl.…”