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Developmental and age-related changes in the D2 dopamine receptor mRNA subtypes in rat brain
1Department of Pharmacology, Medical College of Pennsylvania, Eastern Pennsylvania Psychiatric Institute, Philadelphia.
Abstract:
The influence of ontogeny and aging on the D2 dopamine receptor mRNA in rat brain were examined using in situ hybridization histochemistry and Northern analysis utilizing oligonucleotide probes complementary to the different D2 mRNA subtypes. At birth, there was a high level of D2 dopamine receptor mRNA in corpus striatum relative to that found in the cerebral cortex and other brain areas. The hybridization signal of striatum (using a probe that hybridizes to both the D2A and D2B mRNA) increased during the first two postnatal weeks, reached a peak at day 16, then declined slightly. The D2A mRNA showed a similar distribution and developmental pattern. Intracisternal injection of 6-hydroxydopamine into neonates did not significantly alter the increase of the D2 dopamine receptor mRNAs, suggesting that neuronal input does not influence the ontogenetic development of this mRNA. In striatum, olfactory tubercule and inferior colliculus, the D2A mRNA declined between 3 and 24 months of age. By contrast, there was an age-related increase in the D2A mRNA in the anterior and intermediate lobes of the pituitary. The mRNA for the D2B dopamine receptor showed very low but nevertheless detectable levels in striatum, olfactory tubercule and pituitary. Like with the D2A mRNA, in 24-month-old rats the D2B mRNA declined in striatum and olfactory tubercule and increased in pituitary. These results show that there are differential tissue-related changes in the mRNAs for the D2 dopamine receptor during both development and aging.
Insights
Dopamine D2 receptor mRNA levels in rat brains change significantly during development and aging. These changes vary by brain region and receptor subtype, indicating complex regulation.
Area of Science:
- Neuroscience
- Molecular Biology
- Developmental Biology
Background:
- Dopamine D2 receptors play crucial roles in various brain functions.
- Understanding the regulation of D2 dopamine receptor mRNA is essential for comprehending brain development and aging.
Purpose of the Study:
- To investigate the influence of ontogeny and aging on D2 dopamine receptor mRNA expression in rat brains.
- To analyze the differential expression patterns of D2A and D2B mRNA subtypes across various brain regions and life stages.
Main Methods:
- In situ hybridization histochemistry and Northern analysis were employed.
- Oligonucleotide probes specific to D2A and D2B mRNA subtypes were utilized.
- Expression levels were quantified in different brain regions of rats at various developmental and aging stages.
Main Results:
- D2 dopamine receptor mRNA levels were high at birth in the corpus striatum, peaking around day 16 and then declining.
- Neuronal input, modulated by 6-hydroxydopamine, did not significantly affect the ontogenetic increase of D2 dopamine receptor mRNAs.
- D2A mRNA levels decreased in the striatum, olfactory tubercle, and inferior colliculus with age but increased in the pituitary gland.
- D2B mRNA exhibited similar age-related trends, decreasing in the striatum and olfactory tubercle while increasing in the pituitary.
Conclusions:
- D2 dopamine receptor mRNA expression undergoes significant, tissue-specific changes during rat brain development and aging.
- The distinct developmental and aging patterns of D2A and D2B mRNA subtypes suggest differential regulatory mechanisms.
- These findings highlight the dynamic nature of dopamine receptor gene expression throughout the lifespan.