Fiber connections of the lateral valvular nucleus in a percomorph teleost, tilapia (Oreochromis niloticus)

Abstract

Fiber connections of the lateral valvular nucleus were investigated in a percomorph teleost, the tilapia (Oreochromis niloticus), by tract-tracing methods. Following tracer injections into the lateral valvular nucleus, neurons were labeled in the ipsilateral dorsal part of dorsal telencephalic area, corpus glomerulosum pars anterior, dorsomedial thalamic nucleus, central nucleus of the inferior lobe, mammillary body, semicircular torus, valvular and cerebellar corpus, in the bilateral rostral regions of the central part of dorsal telencephalic area, dorsal region of the medial part of dorsal telencephalic area, habenula, anterior tuberal nucleus, posterior tuberal nucleus, and spinal cord, and in the contralateral lateral funicular nucleus. Labeled fibers and terminals were found in the ipsilateral cerebellar corpus and bilateral valvula of the cerebellum. Tracers were injected into portions of the telencephalon, pretectum, inferior lobe, and cerebellum to confirm reciprocally connections with the lateral valvular nucleus and to determine afferent terminal morphology in the lateral valvular nucleus. Telencephalic fibers terminated mainly in a dorsolateral portion of the lateral valvular nucleus. Terminals from the corpus glomerulosum pars anterior, central nucleus of the inferior lobe, and mammillary body showed more diffuse distributions and were not confined to particular portions of the lateral valvular nucleus. Labeled terminals in the lateral valvular nucleus were cup-shaped or of beaded morphology. These results indicate that the lateral valvular nucleus receives projections from various sources including the telencephalon, pretectum, and inferior lobe to relay information to the valvular and cerebellar corpus. In addition, the corpus glomerulosum pars anterior in tilapia is considered to be homologous to the magnocellular part of superficial pretectal nucleus in cyprinids.

Afferent Connections of the Corpus cerebelli in Holocentrid Teleosts

“…Projections from the pretectum and hypothalamus to the NLV have also been reported in previous studies [Ito and Yoshimoto, 1990;Shimizu et al, 1999;Yang et al, 2004]. The NLV thus may also convey pretectal and hypothalamic inputs to the CC in addition to the telencephalic afferents [Ito and Yoshimoto, 1990;Yang et al, 2004].…”

“…A telencephalic relay portion of the NLV has been regarded as a separated cell group from the NLV, and was called the dorsal tegmental nucleus in some teleosts [Lepomis and Carassius: Wullimann and Northcutt, 1988;Carassius and Pantodon: Wullimann and Meyer, 1993]. Projections from the pretectum and hypothalamus to the NLV have also been reported in previous studies [Ito and Yoshimoto, 1990;Shimizu et al, 1999;Yang et al, 2004]. The NLV thus may also convey pretectal and hypothalamic inputs to the CC in addition to the telencephalic afferents [Ito and Yoshimoto, 1990;Yang et al, 2004].…”

“…These similarities suggest that the CCd and CCv of holocentrids might correspond to lobes C 1 and C 3 of mormyrids, respectively. The NLV relays inputs from the telencephalon to the CC in many teleosts [Wullimann and Northcutt, 1990;Wullimann and Meyer, 1993;Yang et al, 2004]. Fibers from the telencephalon mainly project to the rostralmost portion of the NLV in Gnathonemus [Wullimann and Northcutt, 1990].…”

L-histidine reduces inhibitory avoidance in Carassius auratus submitted to cerebellar ablation

“…Similar findings have been reported in several other studies (10,11,17,18). Thus, we believe that the results for the fish in the A-SAL and S-SAL groups were opposite in terms of memory consolidation of the inhibitory avoidance task due to the absence of cerebellar modulation in limbic structures in the ablation group, especially in the MP, which is thought to be homologous to the amygdala (29)(30)(31).…”

“…The lateral pallium is associated with spatial and temporal memory, and appears to be homologous to the hippocampus of vertebrates, while the medial pallium (MP) is related to emotional memory and has been suggested to be homologous to the amygdala of mammals (28,29). Furthermore, recent studies have demonstrated the existence of connections between the cerebellum and the MP in goldfish and other teleost fish (30,31).…”