An experimental study of the connections of the telencephalon in the rainbow trout (Oncorhynchus mykiss). I: Olfactory bulb and ventral area

Abstract

The fluorescent carbocyanine dye 1,1'-dioctadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) was used in fixed tissue to comprehensively analyze the connections of the olfactory bulbs and the different regions of the ventral (V) area of the telencephalic lobes (subpallium) of the rainbow trout. With this goal, DiI was applied to the different telencephalic nuclei and zones, as well as to the olfactory nerve, the olfactory bulb, the retina, and to several structures in the diencephalon and brainstem of juvenile trout. The olfactory bulbs maintain reciprocal connections with several regions of the telencephalon [ventral nucleus of V (Vv), supracommissural nucleus (Vs), posterior zone of D (Dp), preoptic nucleus], and also project to the diencephalon (posterior tuberal nucleus, posterior hypothalamic lobe). Vv receives afferents from Vs, the dorsal nucleus of V (Vd), the preoptic nucleus, and from several nuclei in the diencephalon and brainstem (suprachiasmatic nucleus, anterior and lateral tuberal nuclei, preglomerular complex, tertiary gustatory nucleus, posterior tubercle, inferior hypothalamic lobes, thalamus, torus semicircularis, secondary gustatory nucleus, locus coeruleus, superior raphe nucleus, central gray, and reticular formation), and projects to dorsal (pallial) regions and most of the nuclei afferent to Vv. The dorsal nucleus of V (Vd) and Vs mainly project to the dorsal area. In an accompanying article (Folgueira et al., 2004), we present the results of application of DiI to dorsal (pallial) telencephalic regions, as well as of several experiments of tracer application to extratelencephalic regions. The results presented here, together with those of the accompanying article, reveal a complex connectional pattern of the rainbow trout ventral telencephalon, most of these connections having not been described previously in salmonids.

The Vertebrate mesolimbic reward system and social behavior network: A comparative synthesis

“…The neurochemical profile is similar to that of mammals except for the apparent absence of choline acetyltransferase-positive or AVT-positive cells (Table 2). Also in support of this homology, this region shares connections with the putative basolateral amygdala (blAMY) homolog as well as many projections to the hypothalamus (Folgueira et al, 2004a).…”

“…However, developmental studies have pointed to the supracommissural part of the ventral pallium (Vs) as the putative homolog of the extended amygdala (the meAMY and BNST), as this region contains the gene markers Dlx2, Lhx7, Nkx2.1b (Table 3) (Alunni et al, 2004). Vs also projects to several hypothalamic regions (Folgueira et al, 2004a), including the anterior tuberal nucleus (putative homolog of the VMH, see subsection for discussion). This region may also be functionally similar to the mammalian meAMY, as stimulation of Vs increases aggression in male bluegill fish (Lepomis macrochirus; Demski and Knigge, 1971), and increases spawning in both male and female sockeye salmon (Oncorhynchus nerka; Satou et al, 1984).…”

“…The medial part of the dorsal telencephalon (Dm) is currently thought to be the putative blAMY homolog. This region receives olfactory input (Folgueira et al, 2004a) as well as other nonchemosensory inputs (Folgueira et al, 2004b), similar to the mammalian blAMY. However, it should be noted that there are subregions of Dm about which little is known in terms of their function.…”

Comparative Analysis of the Organization of the Cholinergic System in the Brains of Two Holostean Fishes, the Florida Gar <b><i>Lepisosteus platyrhincus</i></b> and the Bowfin <b><i>Amia calva</i></b>

“…These subpallial cholinergic cells are considered homologous to one or more septal nuclei or the olfactory tubercle of tetrapods . These subpallial ChAT-ir cells could be the source of the cholinergic innervations in the dorsal telencephalic areas [Murakami et al, 1983;Folgueira et al, 2004]. In lungfishes, ChAT-ir cells are distributed profusely in the caudal lateral septum, caudoventral portion of the striatum, and principally in areas recently characterized as the pallidum and the bed nucleus of the stria terminalis by combinations with specific markers, such as the transcription factor Nkx2.1 [González and Northcutt, 2009;Northcutt, 2009;López et al, 2012].…”

Aluminum exposure impacts brain plasticity and behavior in Atlantic salmon (Salmo salar)

“…Such an effect is likely to have a negative influence on the ability of the fish to cope with the transition from freshwater to the marine environment, a time when the fish need to perform critical behaviors such as predator avoidance, social interactions and navigation Ebbesson and Braithwaite, 2012). Furthermore, it is possible that the reduced forebrain neural plasticity and cognitive deficit at the critical smolt stage also affect imprinting, by altering the olfactory-telencephalic plasticity associated with smoltification (Ebbesson et al, 1996a;Ebbesson et al, 2003;Folgueira et al, 2004). Memories of the natal stream formed during imprinting are later used to return as adults (Hasler and Scholz, 1983;Yamamoto et al, 2010), and thus impaired imprinting could have a profound impact on return success.…”