Forebrain

In the olfactory bulb, numerous moderately labeled cells were found in the internal and external cellular layers, as well as in the glomerular layer (Figure 5a). In the dorsal telencephalon, the expression pattern of NT-6 mRNA was characterized by weak labeling in few scattered neurons of the central nucleus, whereas intense signal probe was observed in dorso-dorsal, medial (Figure 5b) and lateral nuclei. In the ventral telencephalon, NT-6 mRNA weakly labeled few neurons of dorsal and lateral nuclei. In the preoptic area, NT-6 mRNA expression was detected in the anterior (Figure 5c), parvoand magnocellular nuclei, and in the suprachiasmatic nucleus. Intense staining was seen in neurons along third ventricle (Figure 5d). In the pretectal area, strong labeling was observed in numerous neurons of cortical nucleus (Figure 5e,f), as well as in neurons of parvocellular superficial pretectal nucleus. Intense staining was observed in few neurons of supraglomerular nucleus. NT-6 mRNA was observed in several weakly positive neurons of dorsal hypothalamus.

**Figure 5.** Expression of neurotrophin-6 (NT-6) mRNA in transverse section of forebrain of adult *N. furzeri.* On the left side, schematic drawings of *N. furzeri* brain, with red dots indicating NT-6 mRNA distribution over the different brain areas. Forebrain: (**a**) sense probe staining in the Dm and OB; (**b**) positive cells in icl, ecl and gl of olfactory bulbs; (**c**) positive neurons in the dorso-medial and dorso-dorsal zone of dorsal telencephalon; (**d**) numerous and intensely stained neurons in the anterior part of preoptic area; (**e**) intensely stained neurons scattered along the third ventricle; (**f**) sense probe staining in the NC and anterior part of OT; (**g**) overview of pretectal area and anterior part of optic tectum, with strong positive labeling in the neurons of NC; and (**h**) high magnification of positive neurons of NC. Scale bars: (**a**–**c**,**f**) 50 μm; (**d**) 25 μm; and (**e**) 100 μm. Abbreviations: Dd, dorsal zone of dorsal telencephalon; Dm, medial zone of dorsal telencephalon; ecl, external cellular layer; gl, glomerular layer; icl, internal cellular layer; NC, cortical nucleus; OB, olphactory bulb; ON, optic nerve; OT, optic tectum; PPa, anterior preoptic area; III, third ventricle.
