Quantitation of changes in gene expression of norepinephrine biosynthetic enzymes in rat stellate ganglia induced by stress

Abstract

Enzymes involved in catecholamine synthesis are present in the highest concentration in the adrenal medulla, however they were found also in other, mainly nervous tissues. The aim of our study was to quantify the exact concentration of tyrosine hydroxylase (TH) and dopamine-ß-hydroxylase (DBH) mRNA in rat stellate ganglia under control conditions and at different intervals after exposure to immobilization stress (IMO). In rats immobilized once for 2 h, we determined TH and DBH mRNA in different time intervals up to 22 h after the end of the stress stimulus. TH immunoreactive protein levels were also determined in stellate ganglia. TH and DBH mRNA levels were quantified by RT-competitive-PCR. In stellate ganglia, the concentration of TH mRNA was 17±1.6 amol/μg of total RNA, which is approximately 30-times lower than in the adrenal medulla. The concentration of DBH mRNA in the stellate ganglia was 2601±203 amol/μg of total RNA, which is the concentration similar to adrenal medulla, but is 150-times higher than concentration of TH mRNA in stellate ganglia. After a single 2-h immobilization the highest elevation of TH and DBH mRNA levels was meausured 22 h after the termination of the stress stimulus. Repeated immobilization (7 days, 2 h daily) did not produce further increase in TH and DBH mRNA levels compared to already elevated levels in adapted control group (immobilized for 6 days, 2 h daily and decapitated 22 h later). Levels of TH protein were significantly changed only after the repeated immobilization. This study compared for the first time the precise amounts of TH and DBH mRNA in rat stellate ganglia under control conditions and after immobilization stress, and indicates large differences in their concentration. TH and DBH mRNA concentrations in stellate ganglia are markedly elevated for a prolonged period of time after termination of the stress stimuli.