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Selective expression of dopamine D3 receptor mRNA in proliferative zones during embryonic development of the rat
1Laboratoire de Physiologie, Université René Descartes, 75006 Paris, France.
Abstract:
We studied by in situ hybridization histochemistry the expression of D3 receptor (D3R) mRNA at various stages of rat brain development. The first expression of D3R mRNA was detected at embryonic day 14 (E14) in the striatal and rhinencephalic neuroepithelia and throughout the tectal neuroepithelium. From E16 to E19 D3R mRNA expression extended along a rostrocaudal axis to additional proliferative ventricular zones of the basal forebrain, including the neuroepithelia of the olfactory bulb, nucleus accumbens, septum, and amygdala, whereas D1 and D2 receptor (D1R and D2R) mRNAs were expressed predominantly by migrating neuroblasts and/or differentiating striatal neurons. Only a few neuroblasts, migrating in the lateral cortical stream or developing as cerebellar Purkinje cells, expressed D3R mRNA from E18. At birth D3R expression mRNA appeared in differentiating neuronal fields of the nucleus accumbens and medial mamillary body primordia and on P5 reached a distribution similar to that found in adult. In addition, a transient upregulation was detected on P5 in the medial mamillary bodies, parietofrontal cortex, and olfactory tubercle. In the adult brain D3R gene expression continued in the striatal proliferative subventricular zone. The late expression D3R mRNA in neurons, after achievement of dopamine innervation, supports the existence of a regulating factor released from dopamine neurons, as suggested by denervation studies in the adult. The sustained and abundant D3R gene expression, predominantly in germinative neuroepithelial zones actively involved in neurogenesis of most basal forebrain structures, supports the hypothesis of a neurogenetic but minor morphogenetic modulatory role for the D3R during CNS development.
Insights
Dopamine D3 receptor (D3R) mRNA is first detected in embryonic rat brain neuroepithelia, later appearing in developing neurons. Its expression pattern suggests a role in neurogenesis and potentially modulating brain development.
Area of Science:
- Neuroscience
- Developmental Biology
- Molecular Biology
Background:
- Dopamine receptors play crucial roles in brain function.
- Understanding dopamine receptor expression during development is key to deciphering brain formation.
- The D3 receptor's (D3R) developmental expression pattern is not fully elucidated.
Purpose of the Study:
- To investigate the spatio-temporal expression of Dopamine D3 receptor (D3R) mRNA during rat brain development.
- To compare D3R mRNA expression with D1 and D2 receptor (D1R, D2R) mRNA expression patterns.
- To explore the potential role of D3R in neurogenesis and brain development.
Main Methods:
- In situ hybridization histochemistry was employed to detect D3R mRNA expression.
- Analysis was performed across various embryonic and postnatal stages of rat brain development.
- Expression patterns were correlated with neuroepithelial proliferation and neuronal differentiation.
Main Results:
- D3R mRNA was first detected at embryonic day 14 (E14) in neuroepithelia of the striatum, rhinencephalon, and tectum.
- Expression expanded to other basal forebrain proliferative zones by E19, including olfactory bulb, nucleus accumbens, septum, and amygdala.
- In contrast, D1R and D2R mRNAs were primarily found in migrating neuroblasts and differentiating neurons; D3R expression in these cells was limited.
- Postnatally, D3R mRNA appeared in differentiating neurons and showed transient upregulation in specific regions.
- Adult D3R gene expression persisted in the striatal subventricular zone, a site of ongoing neurogenesis.
Conclusions:
- The late expression of D3R mRNA in neurons post-innervation supports a role for dopamine-derived factors.
- Sustained D3R expression in germinative neuroepithelial zones suggests a neurogenetic role.
- D3R may play a minor morphogenetic modulatory role during central nervous system development.
