The habenular complex and its associated axonal pathways are often thought of as phylogenetically conserved features of the brain among vertebrates despite the fact that detailed studies of this brain region are limited to a few species. Here, the gross morphology and axonal projection pattern of the habenular complex of an anuran amphibian, the fire-bellied toad Bombina orientalis, was studied to allow comparison with the situation in other vertebrates. Axonal pathways were traced using biocytin applications in dissected brain preparations. The results show that the rostral part of the left dorsal nucleus is enlarged in this species, while the rostral ventral nucleus and caudal parts do not show left-right size differences. Biocytin applications revealed widespread axonal projections of the habenular complex to the posterior tuberculum/dorsal hypothalamic region, ventral tegmentum, interpeduncular nucleus (IPN), and raphe median. Additionally, axons targeting the lateral hypothalamus originated from the ventral habenular nuclei. The results also suggest an asymmetrical pattern of projection to the IPN in the rostral part of the habenular complex, where the left habenula preferentially targeted the dorsal IPN while the right habenula preferentially targeted the ventral IPN. The caudal habenular nuclei showed no asymmetry of projections as both sides targeted the ventral IPN. Comparison of the habenular complex axonal connectivity across vertebrates argues against strong phylogenetic conservation of the axonal projection patterns of different habenular nuclei.

Keywords:
Amphibians, Habenula, Axons, Biocytin, Anterograde tracing, Retrograde tracing, Asymmetry
1.
Adams JC (1981): Heavy metal intensification of DAB-based HRP reaction product. J Histochem Cytochem 29:775.
2.
Aizawa H, Amo R, Okamoto H (2011): Phylogeny and ontogeny of the habenular structure. Front Neurosci 5:138.
3.
Aizawa H, Bianco IH, Hamaoka T, Miyashita T, Uemura O, Concha ML, Russell C, Wilson SW, Okamoto H (2005): Laterotopic representation of left-right information onto the dorso-ventral axis of a zebrafish midbrain target nucleus. Curr Biol 15:238-243.
4.
Amo R, Aizawa H, Takahoko M, Kobayashi M, Takahashi R, Aoki T, Okamoto H (2010): Identification of the zebrafish ventral habenula as a homolog of the mammalian lateral habenula. J Neurosci 30:1566-1574.
5.
Amo R, Fredes F, Kinoshita M, Aoki R, Aizawa H, Agetsuma M, Aoki T, Shiraki T, Kakinuma H, Matsuda M, Yamazaki M, Takahoko M, Tsuboi T, Higashijima S, Miyasaka N, Koide T, Yabuki Y, Yoshihara Y, Fukai T, Okamoto H (2014): The habenulo-raphe serotonergic circuit encodes an aversive expectation value essential for adaptive active avoidance of danger. Neuron 84:1034-1048.
6.
Andres KH, von Düring M, Veh RW (1999): Subnuclear organization of the rat habenular complexes. J Comp Neurol 407:130-150.
7.
Bianco IH, Wilson SW (2009): The habenular nuclei: a conserved asymmetric relay station in the vertebrate brain. Phil Trans R Soc B 364:1005-1020.
8.
Butler AB, Hodos W (1996): Comparative Vertebrate Neuroanatomy: Evolution and Adaptation. New York, Wiley-Liss.
9.
Concha ML, Wilson SW (2001): Asymmetry of the epithalamus of vertebrates. J Anat 199:63-84.
10.
Díaz C, Puelles L (1992): In vitro HRP-labeling of the fasciculus retroflexus in the lizard Gallotia galloti. Brain Behav Evol 39:305-311.
11.
Distel H, Ebbesson SOE (1981): Habenular projections in the monitor lizard (Varanus benegalensis). Exp Brain Res 43:324-329.
12.
Geisler S, Andres KH, Veh RW (2003): Morphologic and cytochemical criteria for the identification and delineation of individual subnuclei within the lateral habenular complex of the rat. J Comp Neurol 458:78-97.
13.
Guglielmotti V, Fiorino L (1998): Asymmetry in the left and right habenulo-interpeduncular tracts in the frog. Brain Res Bull 45:105-110.
14.
Hennigan K, D'Ardenne K, McClure SM (2015): Distinct midbrain and habenula pathways are involved in processing aversive events in humans. J Neurosci 35:198-208.
15.
Herkenham M, Nauta WJH (1977): Afferent connections of the habenula nuclei in the rat: a horseradish peroxidase study, with a note on the fiber-of-passage problem. J Comp Neurol 173:123-146.
16.
Herkenham M, Nauta WJH (1979): Efferent connections of the habenular nuclei in the rat. J Comp Neurol 187:19-48.
17.
Kemali M, Guglielmotti V (1982): The connections of the frog interpeduncular nucleus (ITP) demonstrated by horseradish peroxidase (HRP). Exp Brain Res 45:349-356.
18.
Kemali M, Guglielmotti V, Gioffré D (1980): Neuroanatomical identification of the frog habenular connections using peroxidase (HRP). Exp Brain Res 38:341-347.
19.
Kemali M, Làzàr G (1985): Cobalt injected into the right and left fasciculi retroflexes clarifies the organization of this pathway. J Comp Neurol 233:1-11.
20.
Kim U (2009): Topographic commissural and descending projections of the habenula in the rat. J Comp Neurol 513:173-187.
21.
Kuan Y-S, Gamse JT, Schreiber AM, Halpern ME (2007): Selective asymmetry in a conserved forebrain to midbrain projection. J Exp Zool 308B:669-678.
22.
Laberge F, Roth G (2007): Organization of the sensory input to the telencephalon in the fire-bellied toad, Bombina orientalis. J Comp Neurol 502:55-74.
23.
Laberge F, Mühlenbrock-Lenter S, Dicke U, Roth G (2008): Thalamo-telencephalic pathways in the fire-bellied toad Bombina orientalis. J Comp Neurol 508:806-823
24.
Lawson RP, Seymour B, Loh E, Lutti A, Dolan RJ, Dayan P, Weiskopf N, Roiser JP (2014): The habenula encodes negative motivational value associated with primary punishment in humans. Proc Natl Acad Sci USA 111:11858-11863.
25.
Matsumoto M, Hikosaka O (2009): Representation of negative motivational value in the primate lateral habenula. Nat Neurosci 12:77-84.
26.
Neary TJ, Northcutt RG (1983): Nuclear organization of the bullfrog diencephalon. J Comp Neurol 213:262-278
27.
Northcutt RG (1995): The forebrain of gnathostomes: in search of a morphotype. Brain Behav Evol 46:275-318.
28.
Puelles L, Milán FJ, Martínez-de-la-Torre M (1996): A segmental map of architectonic subdivisions in the diencephalon of the frog Rana perezi: acetylcholinesterase-histochemical observations. Brain Behav Evol 47:279-310.
29.
Puelles L, Rubenstein JLR (2003): Forebrain gene expression domains and the evolving prosomeric model. Trends Neurosci 26:469-476.
30.
Pyron RA, Wiens JJ (2011): A large-scale phylogeny of Amphibia including over 2,800 species, and a revised classification of extant frogs, salamanders, and caecilians. Mol Phylogenet Evol 61:543-583.
31.
Quina LA, Tempest L, Ng L, Harris JA, Ferguson S, Jhou TC, Turner EE (2015): Efferent pathways of the mouse lateral habenula. J Comp Neurol 523:32-60.
32.
Roth G, Nishikawa KC, Wake DB (1997): Genome size, secondary simplification, and the evolution of the brain in salamanders. Brain Behav Evol 50:50-59.
33.
Schmidt A, Wake MH (1997): Cellular migration and morphological complexity in the caecilian brain. J Morphol 231:11-28.
34.
Stamatakis AM, Stuber GD (2012): Activation of lateral habenula inputs to the ventral midbrain promotes behavioral avoidance. Nat Neurosci 15:1105-1107.
35.
Stephenson-Jones M, Floros O, Robertson B, Grillner S (2012): Evolutionary conservation of the habenular nuclei and their circuitry controlling the dopamine and 5-hydroxytryptophan (5-HT) systems. Proc Natl Acad Sci USA 109:E164-E173.
36.
Villalón A, Sepúlveda M, Guerrero N, Meynard MM, Palma K, Concha ML (2012): Evolutionary plasticity of habenular asymmetry with a conserved efferent connectivity pattern. PLoS One 7:e35329.
37.
Wagner F, Stroh T, Veh RW (2014): Correlating habenular subnuclei in rat and mouse by using topographic, morphological, and cytochemical criteria. J Comp Neurol 522:2650-2662.
38.
Yańez J, Anadon R (1994): Afferent and efferent connections of the habenula in the larval sea lamprey (Petromyzon marinus L.): an experimental study. J Comp Neurol 345:148-160.
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