Elsevier

Neuroscience

Volume 150, Issue 3, 12 December 2007, Pages 625-638
Neuroscience

Neuroanatomy
Distribution of inositol-1,4,5-trisphosphate receptor isotypes and ryanodine receptor isotypes during maturation of the rat hippocampus

https://doi.org/10.1016/j.neuroscience.2007.09.058Get rights and content

Abstract

Activation of inositol-1,4,5-trisphosphate receptors (InsP3Rs) and ryanodine receptors (RyRs) can lead to the release of Ca2+ from intracellular stores and propagating Ca2+ waves. Previous studies of these proteins in neurons have focused on their distribution in adult tissue, whereas, recent functional studies have examined neural tissue extracted from prenatal and young postnatal animals. In this study we examined the distribution of InsP3R isotypes 1–3 and RyR isotypes 1–3 in rat hippocampus during postnatal maturation, with a focus on InsP3R1 because it is most prominent in the hippocampus. InsP3R1 was observed in pyramidal cells and granule cells, InsP3R2 immunoreactivity was observed in perivascular astrocytes and endothelial cells, and InsP3R3 immunoreactivity was detected in axon terminals located in stratum pyramidale of CA1 and microvessels in stratum radiatum. RyR1 immunolabeling was enriched in CA1, RyR2 was most intense in CA3 and the dentate gyrus, and RyR3 immunolabeling was detected in all subfields of the hippocampus, but was most intense in stratum lacunosum-moleculare. During maturation from 2 to 10 weeks of age there was a shift in InsP3R1 immunoreactivity from a high density in the proximal apical dendrites to a uniform distribution along the dendrites. Independent of age, InsP3R1 immunoreactivity was observed to form clusters within the primary apical dendrite and at dendritic bifurcations of pyramidal neurons. As CA1 pyramidal neurons matured, InsP3R1 was often co-localized with the Ca2+ binding protein calbindin D-28k. In contrast, InsP3R1 immunolabel was never co-localized with calbindin D-28k immunopositive interneurons located outside of stratum pyramidale or with parvalbumin, typically found in hippocampal basket cells, suggesting that InsP3R1s do not play a role in internal Ca2+ release in these interneurons. These findings should help to interpret past functional studies and inform future studies examining the characteristics and consequences of InsP3R-mediated internal Ca2+ release and Ca2+ waves in hippocampal neurons.

Section snippets

Animals and tissue preparation

Tissue was obtained from rats (Sprague–Dawley; Charles River, Wilmington, MA, USA) using experimental procedures consistent with those outlined in National Institutes of Health publication 91–3207, Preparation and Maintenance of Higher Animals During Neuroscience Experiments, and approved by the Institutional Animal Care and Use Committee at the Yale University School of Medicine. Every effort was made to minimize the number of animals used and their suffering. Animals were deeply anesthetized

General InsP3R isotype 1–3 immunoreactivity in mature rat hippocampus

Consistent with previous reports (Nakanishi et al 1991, Sharp et al 1993, Sharp et al 1999, Dent et al 1996), InsP3R1 immunoreactivity was found throughout the mature rat hippocampus (>8 weeks old) with the strongest labeling in area CA1 (Figs. 1A and 2A). InsP3R1 immunostaining appeared to be exclusively located in neurons, while InsP3R2 immunoreactivity was only found in a subpopulation of astrocytes (Sharp et al., 1999) and in endothelial cells of capillaries (Fig. 1B). Fine astrocytic

Discussion

In this study we examined the distribution of the intracellular Ca2+ channel proteins InsP3R1-3 and RyR1-3 in the hippocampus of maturing rat. The greatest changes occurred with type 1 InsP3Rs. Because synaptically elicited internal Ca2+ release in hippocampal pyramidal neurons has been reported to depend exclusively on InsP3Rs (Pozzo-Miller et al 1996, Nakamura et al 1999, Kapur et al 2001), we focused our analysis on this protein. Our principal novel findings are the following: (1) during

Acknowledgments

We gratefully acknowledge Constantinos Paspalas for his generous help with this project and for his insightful comments on this manuscript. We thank Rick Matthews for use of his confocal microscope. We also thank John Fitzpatrick for writing our computer analysis software, Anna Hagenston for a critical reading of the manuscript, Amanda Sleeper for her initial help with the experiments, and Keith Gipson for many thoughtful discussions. This research was supported by Whitehall Foundation, Kavli

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    Present address: Department of Neurosurgery Ruprecht-Karls-University Heidelberg, Germany.

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