Retinotectal transmission in the optic tectum of rainbow trout

Abstract

Retinotectal transmission has not yet been well characterized at the cellular level in the optic tectum. To address this issue, we used a teleost, the rainbow trout, and characterized periventricular neurons as postsynaptic cells expected to receive the retinotectal inputs to the optic tectum. The somata of periventricular neurons are localized in the upper zone of the stratum periventriculare (SPV), whereas the lower zone of the SPV comprises the cell body layer of radial glial cells. Ca2+ imaging identified functional ionotropic glutamate receptors in periventricular neurons. We also cloned cDNAs encoding the NR1 subunit of N-methyl-D-aspartic acid (NMDA) receptors and the GluR2 subunit of (+/-)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) receptors, and detected their mRNAs in periventricular neurons by in situ hybridization. The presence of the receptor subunit proteins was also confirmed in the dendrites of periventricular neurons by immunoblotting and immunohistochemistry. On the other hand, radial glial cells in the lower zone of the SPV did not respond to glutamate applications, and mRNA and immunoreactivities of ionotropic glutamate receptors were not detected in glial cells. The present findings suggest that glutamatergic transmission at synapses between retinotectal afferents and periventricular neurons is mediated by the functional NMDA and AMPA receptors.

Cloning and characterization of the N-methyl-D-aspartate receptor subunit NR1 gene from chum salmon, Oncorhynchus keta (Walbaum, 1792)

“…The gene structures of mammalian, tilapia, and zebrafish NR1 genes are similar; however, they differ in terms of the exon coding for the C-terminal domain by spliced variants. For example, the teleost NR1 genes lack the C2 sequence (Bottai et al 19971998; Harvey-Girard and Dunn 2003; Cox et al, 2005; Kinoshita et al 2005). …”

“…NMDARs are heteromers comprising two obligate NMDARs and two NR2 (NR2A-D) or NR3 subunits (NR3A-B) (Cull-Candy and Leszkiewicz 2004). Teleost NMDARs have been cloned from knifefish ( Apteronotus leptorpynchus ), rainbow trout ( O. mykiss ), and zebrafish ( Danio rerio ) (Bottai et al 1997; Harvey-Girard and Dunn 2003; Cox et al 2005; Kinoshita et al 2005). However, in anadromous salmon, only sockeye salmon was registered partial NMDA receptor genes sequence in the NCBI database, but the authors has not published English papers.…”

Long-Term Potentiation Promotes Proliferation/Survival and Neuronal Differentiation of Neural Stem/Progenitor Cells

“…As shown in Fig. 4 A, the vast majority of the isolated cells (labeled with nuclei fluorescent dye DAPI) expressed type IV intermediate filament protein nestin, a protein marker for NPCs [53], and type III intermediate filament protein vimentin, a protein marker for mitotically active [54], neural progenitors [55] and radial glia [56]. Further supporting their identity as immature NSCs, we found that the vast majority of these neurosphere-derived cells did not express MAP2, a protein marker for fully differentiated mature neurons (Fig.…”

Physiological Mechanisms of Imprinting and Homing Migration of Pacific Salmon

“…The NMDAR is a glutamate receptor channel subtype and mediates most of the fast excitatory synaptic transmission in the central nervous system. It plays important roles in memory formation and retrieval in higher vertebrates (Park et al 2013) and in fish (Kinoshita et al 2005;Nam et al 2004;Cox et al 2005;Gómez et al 2006;Tzeng et al 2007;Sison and Gerlai 2011). NMDAR is comprised of two subunits: the essential NR1 subunit and the differentially expressed NR2A-D subunit (Shipton and Paulsen 2013).…”