An atlas of cholinergic innervation in the superior colliculus of the mouse

Authors

• CA Mejias-Aponte
• ZK Joy
• RJ Krauzlis

Abstract

The midbrain superior colliculus (SC) integrates sensory and motor information for salient environmental response. The superficial (sSC) is a primary recipient of retinal input, while the intermediate (iSC) receives visual and other sensory inputs and coordinates motor outputs. We are interested in whether different neurotransmitter markers can produce selective demarcation of different SC subregions. We selected cholinergic innervation (CI) as a putative target, as these axons' expression and distribution are relatively conserved across species. We used immunohistochemistry of vesicular acetylcholine transporter to map CI distribution in the mouse brain. In the sSC, the anterior colliculus shows a dense, continuous band of fibers in the superficial gray layer (SGL). In the middle SC, fiber density decreases laterally within the SGL and zonal layers. In the posterior SC, CI expression is sparser and without a distinct SGL band. In the iSC, fiber density increases from the anterior to posterior axis. The anterior and middle colliculus display a patchy fiber distribution, denser medially and more diffuse laterally. The posterior SC has two fiber bands in the intermediate gray and white layers, which thin laterally. Where the SC is flanked by the inferior colliculus, these bands are uniformly dense across the mediolateral axis. Our findings establish that expression is not uniform throughout the SC, and we are currently working on quantifying the density of CI distribution to determine whether there are subregion differences.

Scientific Focus Area: Neuroscience

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