Ontogeny of somatostatin mRNA-containing perikarya in the rat central nervous system
S Fitzpatrick-McElligott1, J P Card, T M O'Kane
1Medical Products Department, E.I. du Pont de Nemours and Co., Wilmington, Delaware 19898.
Abstract:
The distribution of neuronal perikarya containing somatostatin mRNA in the developing rat brain was investigated with in situ hybridization histochemistry. This study describes the expression of somatostatin mRNA during selected perinatal stages and demonstrates regional changes in somatostatin mRNA expression at the single cell level. The mRNA expression closely parallels previously reported developmental localization of the peptide (Inagaki et al., 1982; Shiosaka et al., 1982). As early as embryonic day 13 (E13), somatostatin mRNA was observed in discrete spinal cord and brainstem regions. At birth, densely hybridized somata could be seen primarily in ventral and caudal brain areas with small scattered neurons in the hippocampus and dorsal neocortex. After birth, somatostatin mRNA increased in forebrain regions, such as the hippocampus, dorsal neocortex, and caudate. By postnatal day 14 (P14), the distribution in the telencephalic and diencephalic regions approached that of the adult brain. Several brain regions manifested large changes in the density of somatostatin mRNA hybridization during development. For example, the cerebellar vermis and brainstem contained somatostatin mRNA perikarya during early postnatal development but decreased in these regions in the adult. During perinatal development, increases in somatostatin mRNA content were the results of increases in both the number of neurons containing somatostatin mRNA as well as in the amount of this mRNA expressed in each cell. As the brain differentiates, the apparent numbers of somatostatin mRNA containing neurons in certain brain regions are reduced. These data provide evidence for transient somatostatinergic neurons during early development in discrete areas of the occipital cortex, pyriform cortex, cerebellum, and brainstem and suggest that this peptide may play a role in the development of these regions.
Insights
This study maps somatostatin mRNA in the developing rat brain, revealing transient expression in specific regions like the cerebellum and brainstem during early development. These findings suggest a role for somatostatin in neural development.
Area of Science:
- Neuroscience
- Developmental Biology
- Molecular Biology
Background:
- Somatostatin is a neuropeptide with diverse functions in the central nervous system.
- Its developmental expression patterns are crucial for understanding brain maturation.
- Previous studies have localized the somatostatin peptide during development.
Purpose of the Study:
- To investigate the spatiotemporal distribution of somatostatin mRNA in the developing rat brain.
- To identify regional changes in somatostatin mRNA expression at the single-cell level during perinatal stages.
- To correlate mRNA expression with known peptide localization during development.
Main Methods:
- In situ hybridization histochemistry was used to detect somatostatin mRNA.
- Analysis focused on selected perinatal stages of the rat brain.
- Quantitative assessment of mRNA hybridization in neuronal perikarya was performed.
Main Results:
- Somatostatin mRNA was detected as early as embryonic day 13 in the spinal cord and brainstem.
- At birth, expression was prominent in ventral/caudal brain areas, hippocampus, and neocortex.
- Expression increased in forebrain regions postnatally, approaching adult distribution by postnatal day 14.
- Transient expression was observed in the cerebellar vermis and brainstem, decreasing in adults.
- Increases in mRNA content resulted from both increased neuron numbers and per-cell expression.
- Apparent neuron numbers decreased in some regions during differentiation.
Conclusions:
- Somatostatin mRNA distribution during development parallels peptide localization.
- Evidence suggests transient somatostatinergic neurons play a role in early brain development.
- These transient neurons are found in specific areas like the occipital cortex, pyriform cortex, cerebellum, and brainstem.
- Somatostatin may be involved in the developmental processes of these brain regions.
