Differential regulation of short and long dopamine D2 receptor mRNA levels by hypoxia in the adrenals of 1-day-old and adult rabbits

Abstract

We tested the hypothesis that hypoxic exposure exerts distinct modulation on the mRNA level of the short and long isoform of the D2 dopamine (DA) receptor (D 2r) and on tyrosine hydroxylase (TH) in the adrenals and superior cervical ganglion (SCG) of 1-day-old and adult rabbits. One-day-old and adult rabbits have been exposed to moderate (FiO 2: 0.15) or severe (FiO 2: 0.08) hypoxia for 0 (control), 6 or 24 h. At the end of the hypoxic exposure, the adrenals and SCG were rapidly dissected and kept frozen. Standard procedure for Northern blot and RT-PCR for evaluation of the short (D 2S) or long (D 2L) isoform of D 2r and TH have been used. In the adrenals of adult rabbits, moderate and severe hypoxia decreased the D 2S and D 2L mRNA with a more prominent effect on the short isoform and increased TH mRNA. In 1-day-old rabbits, changes of D 2r and TH mRNA levels were observed only after 24 h of severe or moderate hypoxic exposure and only the D 2S receptor mRNA was significantly reduced. In the SCG, the expression level of both TH and D 2r mRNA were not affected by hypoxic exposure in adult and newborn rabbits. Hence, sustained hypoxic exposure exerts distinct changes on mRNA level of D 2r isoform and TH in an age- and tissue-dependent pattern.