CATECHOLAMINES IN FETAL AND NEWBORN RAT BRAIN

TLDR

A radiometric‑enzymatic assay was developed that converts dopamine and norepinephrine to 3‑O‑methyl derivatives using catechol‑O‑methyl transferase and [3H]‑SAM, then isolates them by selective extraction. The assay detected both amines as low as 100 pg, showing their presence at 15 days gestation and a 15‑fold increase during the last week, with regional patterns matching biosynthetic enzyme distribution and drug studies indicating adult‑like regulatory controls.

Abstract

Abstract The levels of dopamine and norepinephrine were determined in the brains of fetal and newborn rats by means of a sensitive, radiometric‐enzymatic assay. Catecholamines were converted to their 3‐ O ‐methylated derivatives in the presence of catechol‐ O ‐methyl transferase (EC 2.1.1.1) and [ 3 H‐methyl]S‐adenosylmethionine; and the [ 3 H]‐derivatives were isolated by selective extraction. The assay had a sensitivity for dopamine and norepinephrine of 100 picograms and was linear to at least 30 nanograms of catecholamines. Both amines were present at 15 days of gestation and increased 15‐fold in content during the last week of gestation. The regional distribution of these neurotransmitters in the brain of the newborn rat correlated with the distribution of their biosynthetic enzymes. An investigation of the effects of reserpine, pheniprazine, α‐methyl‐ para ‐tyrosine, diethyldithiocarbamate and l ‐DOPA on the levels of dopamine and norepinephrine in the brains of the 18‐day gestational fetus indicated that the levels of these neurotransmitters are under controls similar to those known to occur in the brain of the adult rat.