Expression of calcium-binding proteins in the proliferative zones around the corticostriatal junction of rabbits during pre- and postnatal development

Pattern of calbindin-D28k and calretinin immunoreactivity in the brain of Xenopus laevis during embryonic and larval development

The present study represents a detailed spatiotemporal analysis of the localization of calbindin-D28k (CB) and calretinin (CR) immunoreactive structures in the brain of Xenopus laevis throughout development, conducted with the aim to correlate the onset of the immunoreactivity with the development of compartmentalization of distinct subdivisions recently identified in the brain of adult amphibians and primarily highlighted when analyzed within a segmental paradigm. CR and CB are expressed early in the brain and showed a progressively increasing expression throughout development, although transient expression in some neuronal subpopulations was also noted. Common and distinct characteristics in Xenopus, as compared with reported features during development in the brain of mammals, were observed. The development of specific regions in the forebrain such as the olfactory bulbs, the components of the basal ganglia and the amygdaloid complex, the alar and basal hypothalamic regions, and the distinct diencephalic neuromeres could be analyzed on the basis of the distinct expression of CB and CR in subregions. Similarly, the compartments of the mesencephalon and the main rhombencephalic regions, including the cerebellum, were differently highlighted by their specific content in CB and CR throughout development. Our results show the usefulness of the analysis of the distribution of these proteins as a tool in neuroanatomy to interpret developmental aspects of many brain regions.

Regional distribution of calretinin and calbindin-D28k expression in the brain of the urodele amphibian Pleurodeles waltl during embryonic and larval development

The sequence of appearance of calretinin and calbindin-D28k immunoreactive (CRir and CBir, respectively) cells and fibers has been studied in the brain of the urodele amphibian Pleurodeles waltl. Embryonic, larval and juvenile stages were studied. The early expression and the dynamics of the distribution of CBir and CRir structures have been used as markers for developmental aspects of distinct neuronal populations, highlighting the accurate extent of many regions in the developing brain, not observed on the basis of cytoarchitecture alone. CR and, to a lesser extent, CB are expressed early in the central nervous system and show a progressively increasing expression from the embryonic stages throughout the larval life and, in general, the labeled structures in the developing brain retain their ability to express these proteins in the adult brain. The onset of CRir cells primarily served to follow the development of the olfactory bulbs, subpallium, thalamus, alar hypothalamus, mesencephalic tegmentum, and distinct cell populations in the rhombencephalic reticular formation. CBir cells highlighted the development of, among others, the pallidum, hypothalamus, dorsal habenula, midbrain tegmentum, cerebellum, and central gray of the rostral rhombencephalon. However, it was the relative and mostly segregated distribution of both proteins in distinct cell populations which evidenced the developing regionalization of the brain. The results have shown the usefulness in neuroanatomy of the analysis during development of the onset of CBir and CRir structures, but the comparison with previous data has shown extensive variability across vertebrate classes. Therefore, one should be cautious when comparing possible homologue structures across species only on the basis of the expression of these proteins, due to the variation of the content of calcium-binding proteins observed in well-established homologous regions in the brain of different vertebrates.

Colocalization of neuropeptides with calcium-binding proteins in the claustral interneurons during postnatal development of the rat

The claustrum is a relatively large telencephalic structure, situated close to the border of the neo- and allocortical regions. Its neuronal population consists of glutamatergic, projecting neurons and GABA-ergic interneurons, characterized by occurrence of numerous additional biochemical markers. The postnatal development of these latter neurons has not been extensively studied. Revealing the characteristic patterns of colocalizations between selected markers may shed some light on their function and origin. We investigated the colocalization patterns between three neuropeptides: neuropeptide Y, somatostatin, vasoactive intestinal polypeptide and three calcium-binding proteins: calbindin D28k, calretinin, parvalbumin in the interneurons of the rat claustrum during a four-month postnatal period (P0-P120; P: postnatal day). Our studies revealed the following types of colocalizations: neuropeptide Y with calbindin D28k, calretinin or parvalbumin; somatostatin with calbindin D28k; vasoactive intestinal polypeptide with calretinin. Only vasoactive intestinal polypeptide- and calretinin-containing, double-labeled neurons were present at the day of birth, whereas the other double-labeled neurons appeared at later stages of development. The ratios of colocalizing neurons to single-labeled neurons in each type of colocalization were differentiated and reached the highest value (51%) for vasoactive intestinal polypeptide- and calretinin-double-labeled neurons. In conclusion, the claustral interneurons represent differentiated population in respect to the occurrence of neuropeptides and calcium-binding proteins. The expression of studied substances is changing during the postnatal period.