Effect of immobilization stress on gene expression of catecholamine biosynthetic enzymes in heart auricles of socially isolated rats

Chronic stress is associated with the development of cardiovascular diseases. The sympathoneural system plays an important role in the regulation of cardiac function both in health and disease. In the present study, the changes in gene expression of the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), dopamine-â-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) and protein levels in the right and left heart auricles of naive control and long-term (12 weeks) socially isolated rats were investigated by Taqman RT-PCR and Western blot analysis. The response of these animals to additional immobilization stress (2 h) was also examined. Long-term social isolation produced a decrease in TH mRNA level in left auricles (about 70 percent) compared to the corresponding control. Expression of the DBH gene was markedly decreased both in the right (about 62 percent) and left (about 81 percent) auricles compared to the corresponding control, group-maintained rats, whereas PNMT mRNA levels remained unchanged. Exposure of group-housed rats to acute immobilization for 2 h led to a significant increase of mRNA levels of TH (about 267 percent), DBH (about 37 percent) and PNMT (about 60 percent) only in the right auricles. Additional 2-h immobilization of individually housed rats did not affect gene expression of these enzymes in either the right or left auricle. Protein levels of TH, DBH and PNMT in left and right heart auricles were unchanged either in both individually housed and immobilized rats. The unchanged mRNA levels of the enzymes examined after short-term immobilization suggest that the catecholaminergic system of the heart auricles of animals previously exposed to chronic psychosocial stress was adapted to maintain appropriate cardiovascular homeostasis.

Analysis of polymorphisms in the dopamine beta hydroxylase gene: association with attention deficit hyperactivity disorder in Indian children.

OBJECTIVE: To study the association of Attention Deficit Hyperactivity Disorder (ADHD) and polymorphism in the dopamine beta hydroxylase (DBH) gene in Indian ADHD cases. SUBJECTS: Forty one ADHD cases were diagnosed as per the DSM-IV-TR criteria and evaluated by Conners Parents and Teachers Rating Scale and Wechslers Intelligence Scale for Children. METHODS: Genomic DNA was amplified for exon 2 *444g/a and intron 5 (Taq I) polymorphism in the DBH gene followed by restriction fragment length polymorphism (RFLP) analysis. Haplotype-based haplotype relative risk (HHRR) was analyzed to ascertain the transmission pattern of these two polymorphisms in ADHD cases. Linkage disequilibrium (LD) between the two polymorphisms was calculated using EH+ and 2LD programs. RESULTS: In the limited number of samples analyzed, a slight increase in transmission of the 444a allele in ADHD subjects was observed for DBH 444g/a. The intron 5 (Taq I) polymorphism showed no significant association with ADHD in these cases. Strong disequilibrium was observed between DBH444g/a and intron 5 (Taq I) polymorphism. CONCLUSION: This is the first molecular genetic study on ADHD in Indian subjects exploring transmission of polymorphisms in the DBH gene. Preliminary investigation shows a trend towards association between the transmission of DBH444a allele and ADHD. No association was noticed between transmission of intron 5 (Taq I) polymorphism and ADHD in the Indian subjects. Presence of strong LD may point towards co-segregation of these two polymorphisms more often than expected.