Figure 8.

Examples of anterograde axonal labeling (AAV-tdTomato) arising from unilateral tracer injections in the LPO (#181221–04A) and LHAa (#181221–02A). (a and b) Dense ipsilateral, and substantial contralateral, innervation of the lateral habenula (LH) from LPO (a), and even denser input from the LHAa (b) at a more caudal LH level. (c and d) A substantially stronger input to ventromedial hypothalamic nucleus anterior part (VMHa) from LHAa (d, and outset) compared to LPO (c) (note the absence of a contralateral VMHa input from either region). Also at this level, substantial axonal labeling is apparent in the LHA laterally adjacent to the VMHa (see Figure 1l for the mouse brain reference atlas level and Figure 1f for rat LHA parcellation at a corresponding atlas level). (e and f) Similar very dense ipsilateral labeling of the medial septal (MS) and diagonal band (NDB) nuclei; comparatively weaker labeling is also present in the lateral septal nucleus (LS). Dashed lines indicate approximate cytoarchitectural boundaries corresponding to reference atlas parcellation. Additional abbreviations: DG, dentate gyrus; fr, fasciculus retroflexus; MH, medial habenula; sm, stria medullaris; V3, third ventricle. Scale bars are 500 μm (a,b,d,e), 250 μm (c,d).