Age-related modulation of dopamine d1 receptor mRNA level by hypoxia in rabbit adrenal gland.

In the perinatal period, the fetus and the neonate may be exposed to hypoxic conditions. The adrenal gland responds to systemic hypoxia by releasing catecholamines. Dopamine and dopamine D1 receptor are present in the adrenal medulla and are liable to be affected by exposure to hypoxia. We used a rabbit model to determine whether hypoxia modulates the dopamine D1 receptor (DA D1-R) mRNA expression in adrenal glands during development. Rabbits were investigated according to four different hypoxic conditions: 15% O2 for 6 h, 15% O2 for 24 h, 8% O2 for 6 h, and 8% O2 for 24 h. Control groups were maintained in normoxic conditions (21% O2). For each O2 condition, animals were studied at three different ages: 1-day old newborns, 25-day-old pups, and 6-month-old adults. We compared the hypoxic groups to their respective age normoxic group. We have shown that hypoxia decreases DA D1-R mRNA expression level, evaluated using Northern blot analysis, in newborn rabbits, whatever the duration and severity of hypoxia. This downmodulation was not observed in 25-day-old and in adult rabbits. This age-related modulation of adrenal DA D1-R mRNA could be linked to the age-related transition from the non-neurogenic to the neurogenic regulation of the adrenal function.