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Postnatal development of calbindin and parvalbumin immunoreactivity in the thalamus of the rat
C Frassoni1, M Bentivoglio, R Spreafico
1Neurological Institute C. Besta, Milan, Italy.
Insights
The study shows that calbindin-D28k (CB) and parvalbumin (PV) mature in rat thalamus over three weeks post-birth. Their distribution and density change, indicating a prolonged developmental period for these key calcium-binding proteins.
Area of Science:
- Neuroscience
- Developmental Biology
- Calcium-Binding Proteins
Background:
- The thalamus is a critical relay center in the brain.
- Calcium-binding proteins like calbindin-D28k (CB) and parvalbumin (PV) play vital roles in neuronal function.
- Their developmental trajectories in the early postnatal period are not fully understood.
Purpose of the Study:
- To investigate the postnatal maturation of CB and PV in the rat thalamus.
- To characterize the developmental changes in the distribution and density of CB and PV.
- To determine the timeline for achieving mature expression patterns of these proteins.
Main Methods:
- Immunohistochemistry was used to visualize CB and PV.
- The study focused on the first three postnatal weeks in rat thalamus.
- Quantitative analysis of protein expression and distribution was performed.
Main Results:
- CB expression increased progressively, following a mediolateral gradient, with mature patterns by week 3.
- PV-immunoreactive fibers showed increased density postnatally with a lateromedial gradient.
- A transient PV hyperinnervation was observed in specific thalamic nuclei during the second postnatal week.
Conclusions:
- Maturation of CB and PV in the rat thalamus is a prolonged postnatal process.
- The distinct developmental patterns suggest differential roles in thalamic neuronal maturation.
- These findings provide insights into the developmental neurobiology of the thalamus.
Abstract:
The maturation of the calcium binding proteins calbindin-D28k (CB) and parvalbumin (PV) during the first 3 postnatal weeks was studied in the rat thalamus using immunohistochemistry. These two proteins display a non-homogeneous distribution in the adult thalamus. In the rat, CB is mainly localized in the neurons and neuropil of the thalamic midline, intralaminar, and ventromedial nuclei, as well as in the posterior complex. At birth, CB-immunoreactive cell bodies were evident in thalamic midline structures, and especially in the nucleus reuniens. The number of thalamic CB-positive cell bodies, as well as the intensity of the neuropil immunostaining, increased progressively in the first postnatal weeks. This quantitative increase was first apparent in the midline structures and then in the other thalamic territories which are CB-positive in adulthood, and followed a mediolateral gradient. The mature pattern was achieved by the end of the third postnatal week. In the adult rat thalamus the neurons of the reticular nucleus display PV-immunostaining and PV-positive fibers densely innervate most of the dorsal thalamic domains. PV-immunoreactivity was clearly evident at birth in the cell bodies of the reticular nucleus. The density of PV-containing fibers increased progressively after birth in the dorsal thalamus, with a lateromedial gradient. At the end of the third postnatal week the ventroposterior (VP) complex appeared heavily innervated by PV-positive fibers, whose density in more medial structures was still lower than in the adult thalamus. A transient hyperinnervation of PV-immunoreactive fibers, displaying a dishomogenous organization in distinct segments, was observed in VP, and especially in the ventroposteromedial nucleus, during the second postnatal week. Altogether these findings indicate that the maturation of CB and PV requires postnatally a relatively prolonged period of time. The possible involvement of these proteins in different functional aspects of thalamic neuronal maturation is discussed.