Immunocytochemical and ultrastructural study of the rat perireticular thalamic nucleus during postnatal development

Abstract

The perireticular thalamic nucleus (PRT) consists of scattered neurons that are located in the internal capsule adjacent to the gamma aminobutyric acid (GABA)-immunoreactive (ir) reticular thalamic nucleus (RT) and whose number decreases during development. The common feature of PRT neurons in different species is the immunoreactivity for the calcium binding protein parvalbumin (PV), which is also expressed by RT cells. In this study, we analyzed, at the light and electron microscopic level, the distribution and morphology of PV-ir neurons and their relationship with GABA in adult and developing rats. We found that the rostrocaudal distribution and the morphology of PV-ir neurons of the PRT were different at each stage of postnatal development examined. The adult configuration of the PV-ir population in the PRT was achieved at postnatal day 21. With electron microscopy, the developing PRT was observed to contain PV-ir neuronal cell bodies and dendrites contacted by several PV-negative synaptic terminals, some of which were GABA-ir, whereas the adult PRT contained also large PV-ir boutons, generally GABA-ir. Very few GABA-ir neurons were found in the PRT region and only during the first postnatal week, thus indicating that the PV-ir neurons of PRT represent a distinct population from those of RT. Our results demonstrate a morphological, neurochemical, and ultrastructural complexity of the PRT not only during development, but also in adulthood. These findings provide new data supporting the suggested roles of the PRT during postnatal development, and may indicate that in adult life it can play other so far unknown functions.

GABAergic parvalbumin-immunoreactive large calyciform presynaptic complexes in the reticular nucleus of the rat thalamus

“…Presence of calcium-binding proteins such as calbindin, parvalbumin and calretinin, have been described in the RTN by Frassoni et al (1991), Spreafico et al (1991), Clemence and Mitrofanis (1992), Resibois and Rogers (1992), Winsky et al (1992), Lizier et al (1997), Amadeo et al (1998), FitzGibbon et al (2000 and Kakei et al (2001). Calcium binding proteins may exert significant action on membrane potential, synaptic transmission and even on the firing pattern of the related neurons (Baimbridge et al, 1992;Caillard et al, 2000).…”

Does the perireticular thalamic nucleus project to the neocortex?

“…has many more neurones) than in the adult. With subsequent maturity, the perireticular nucleus becomes reduced in size -by about P (postnatal day) 10 in rats and ferrets -largely by a process of cell death, and only a few neurones remain in the adult (see Mitrofanis 1992a;Adams and Baker 1995;Earle and Mitrofanis 1996; Ramcharan and Guillery 1997;Amadeo et al 1998).…”

“…has many more neurones) than in the adult. With subsequent maturity, the perireticular nucleus becomes reduced in size -by about P (postnatal day) 10 in rats and ferrets -largely by a process of cell death, and only a few neurones remain in the adult (see Mitrofanis 1992a;Adams and Baker 1995;Earle and Mitrofanis 1996; Ramcharan and Guillery 1997;Amadeo et al 1998).During the early stages of development, several studies have shown that although perireticular neurones are labelled from the dorsal thalamus during prenatal development in rats and ferrets, there are many more perireticular neurones labelled during neonatal development (Mitrofanis and Baker 1993;Mitrofanis 1994b). Thus the perireticular projection is heaviest after birth, well after the early connections of the developing forebrain are complete (reviewed Molnàr and Blakemore 1995).…”

Morphological study of the perireticular nucleus in human fetal brains

“…These neurons are all generated relatively early in development, and show heavy neuronal loss during later development. The neurons of the perireticular nucleus at early embryonal stages express the same antigens (parvalbumin, pro‐α‐thyrotropin releasing hormone calbindin and GABA+) as the neurons in the reticular nucleus (Mitrofanis, 1992a; Letinic & Kostovic, 1996; Amadeo et al. 1998; Contreras‐Rodriguez et al.…”