Calcium-binding protein immunoreactivity in Gudden's tegmental nuclei and the hippocampal formation: differential co-localization in neurons projecting to the mammillary bodies.

Christopher M Dillingham,Seralynne D Vann,Nicholas F Wright,John P Aggleton,Jonathan T Erichsen,Joshua D Holmes

doi:10.3389/fnana.2015.00103

Christopher M Dillingham, Seralynne D Vann + Show 4 more

Open Access

https://doi.org/10.3389/fnana.2015.00103

Copy DOI

Journal: Frontiers in neuroanatomy	Publication Date: Aug 4, 2015
Citations: 10	License type: cc-by

Affiliation: Cardiff University

Abstract

The principal projections to the mammillary bodies arise from just two sites, Gudden’s tegmental nuclei (dorsal and ventral nuclei) and the hippocampal formation (subiculum and pre/postsubiculum). The present study sought to compare the neurochemical properties of these mammillary body inputs in the rat, with a focus on calcium-binding proteins. Neuronal calretinin (CR) immunoreactivity was sparse in Gudden’s tegmental nuclei and showed no co-localization with neurons projecting to the mammillary bodies. In contrast, many of the ventral tegmental nucleus of Gudden cell that project to the mammillary bodies were parvalbumin (PV)-positive whereas a smaller number of mammillary inputs stained for calbindin (CB). Only a few mammillary body projection cells in the dorsal tegmental nucleus of Gudden co-localized with PV and none co-localized with CB. A very different pattern was found in the hippocampal formation. Here, a large proportion of postsubiculum cells that project to the mammillary bodies co-localized with CR, but not CB or PV. While many neurons in the dorsal and ventral subiculum projected to the mammillary bodies, these cells did not co-localize with the immunofluorescence of any of the three tested proteins. These findings highlight marked differences between hippocampal and tegmental inputs to the rat mammillary bodies as well as differences between the medial and lateral mammillary systems. These findings also indicate some conserved neurochemical properties in Gudden’s tegmental nuclei across rodents and primates.

Highlights

The mammillary bodies comprise one of a set of brain structures thought to be vital for human event memory (Dusoir et al, 1990; Vann and Aggleton, 2004; Tsivilis et al, 2008; Vann et al, 2009)
Attention focused on three different calcium-binding proteins, parvalbumin (PV), calbindin (CB), and calretinin (CR), which all bind Ca2+ with a high-affinity, acting as intracellular calcium buffers (Celio, 1990; Andressen et al, 1993). These calcium-binding proteins are expressed in specific subsets of neurons and often do not co-localize with one another, making them a useful tool for differentiating functional pathways (e.g., Rogers and Resibois, 1992; Gritti et al, 2003)
Dorsal Tegmental Nucleus of Gudden (DTg) – Calcium-Binding Proteins Both cellular and neuropillar immunoreactivity to PV were present within dorsal tegmental nucleus (DTg), clearly defining the boundary of the nucleus from neighboring tegmental and raphe nuclei

Summary

Introduction

The mammillary bodies comprise one of a set of brain structures thought to be vital for human event memory (Dusoir et al, 1990; Vann and Aggleton, 2004; Tsivilis et al, 2008; Vann et al, 2009). The principal inputs to the Neurochemistry of mammillary body inputs mammillary bodies in both rodents and primates come from just two sites: (1) the hippocampal formation (Nauta, 1956; Swanson and Cowan, 1977; Aggleton et al, 2005) and (2) Gudden’s tegmental nuclei (Hayakawa and Zyo, 1984; Allen and Hopkins, 1989; Saunders et al, 2012). Both sets of inputs are thought to contribute to learning and memory, but in fundamentally different ways (Vann, 2010). These calcium-binding proteins are expressed in specific subsets of neurons and often do not co-localize with one another, making them a useful tool for differentiating functional pathways (e.g., Rogers and Resibois, 1992; Gritti et al, 2003)

Methods

Results

Discussion

Conclusion