Relationship Between Phenolamines and Catecholamines During Rat Brain Embryonic Development In Vivo and In Vitro

The activities of the catecholamine synthetic enzymes tyrosine hydroxylase and phenylethanolamine N-methyltransferase, and the concentrations of the catecholamines and their respective metabolites, have been measured in the dorsal and ventral halves of the brainstem at various ages in the embryonic and adult rat. The activity of phenylethanolamine N-methyltransferase in both parts of the brainstem at day 14 of gestation is at or greater than adult levels and thereafter displays relatively small variations during ontogeny. Tyrosine hydroxylase activity, in contrast, is undetectable at day 14 and increases slowly, achieving only 20-25% of adult values by day 18 of gestation. Adrenaline concentrations correlate well with the activity of phenylethanolamine N-methyltransferase, showing a precocious development, whereas noradrenaline and 3,4-dihydroxyphenylethylamine (dopamine) concentrations are more closely related to the enhancement of tyrosine hydroxylase activity; at day 18 of gestation, for example, they are only 5 and 10%, respectively, of the adult values. The concentrations of the metabolites of noradrenaline and dopamine are suggestive of a high rate of turnover. These results confirm previous immunocytochemical evidence of a tardy appearance of tyrosine hydroxylase-like immunoreactivity in the phenylethanolamine N-methyltransferase-positive perikarya of the embryonic medulla oblongata. In addition, the abundance of adrenaline in this area at early gestational stages strongly suggests that, despite the paucity of tyrosine hydroxylase, phenylethanolamine N-methyltransferase is active in vivo and is utilizing a substrate other than noradrenaline. It is likely, however, that at later stages of gestation, when tyrosine hydroxylase is present at sufficient activity to supply noradrenaline, the conventional synthetic pathway for adrenaline formation comes into being.

Section: Discussionmentioning

confidence: 69%

“…2), L-aromatic acid decarboxylase (DDC) and dopamine @-hydroxylase (DBH), are present in the medulla oblongata at day 14 of gestation (David, 1984). In addition, their substrates are also present at high concentrations (Saavedra et al, 1974a;David, 1984). The activity in the embryo of the MFO, however, is, at present, unknown.…”

Section: Discussionmentioning

confidence: 99%

Abundance in the Embryonic Brainstem of Adrenaline During the Absence of Detectable Tyrosine Hydroxylase Activity

Foster

Sundström

Helmer-Matyjek

et al. 1987

“…These authors found that OA and phenylethanolamine concentrations increased in the brain at day 15, and then decreased to very low levels afterwards. Recently, it was found that the OA peak is the para isomer and that it occurs in the embryonic hypothalamus (David, 1984).…”

Section: Discussionmentioning

confidence: 99%

“…Because the genetic approach proved to be fruitful, it was used as the basis of the present experiments, the purpose of which was to study i n Roman strains the ontogeny of OA, DA, and NA, as well as some of their metabolic and biosynthesis enzymes. Previous data on unselected rats David, 1984) indicate that the two groups of amines have a differential evolution which may clarify their biochemical and functional relationships in the mammalian brain.…”

mentioning

confidence: 96%

Prenatal Ontogenesis of Brain Phenolamines and Catecholamines in Relation to Their Metabolizing Enzymes in Roman Avoider Strains of Rats

Coulon

Cavoy

Delacour

et al. 1989

Phenolamines, particularly octopamines, are of special importance in avoidance behavior. In the Roman low avoidance (RLA) strain, p-octopamine can induce locomotor behavioral activity that is normally observed in the Roman high avoidance (RHA) strain. For these reasons, the levels of prenatal octopamines (para and meta isomers) have been studied in relation to noradrenaline and dopamine levels. In the hypothalamus and brainstem of RHA, a maximum level of the para isomer is observed at 15 days of embryonic development but, unlike in controls and RLA animals, this level remains almost constant until 20 days. For the meta-isomer and catecholamines, there is a 1-2 day delay in detection between controls and RLA or RHA. The study of related enzyme activities reveals that tyrosine hydroxylase displays a 2-day delay in RHA when compared to the control value at 19 days of fetal life. These results are discussed in terms of the role of p-octopamine in avoidance conditioning and of the possible delayed expression of the tyrosine hydroxylase gene in Roman strains of rats.

“…Among the enzymes involved in the biosynthesis of catecholamines, TH is specific for the catecholamine pathway and is the rate-limiting step (Nagatsu, 1964). The others, like aromatic L-amino-acid decarboxylase (AADC) and DBH, are more ubiquitous and are also involved in the biosynthesis of phenolamines (Brandau and Axelrod, 1972;David, 1984;David et al, 1984). During development of rat brain, the two phenolamine and catecholamine pathways appear to be sequentially represented, first phenolamine from 13 to 15 days and catecholamine after 14.5 days (Coyle and Henry, 1973).…”

mentioning

confidence: 99%

Gene Expression of Tyrosine Hydroxylase in the Developing Fetal Brain

Coulon

Biguet

Cavoy

et al. 1990

Self Cite

Tyrosine hydroxylase, aromatic L-amino-acid decarboxylase, and dopamine beta-hydroxylase activities were studied in the developing fetal rat brain. A delay of 2-3 days between the detection of the tyrosine hydroxylase and the aromatic L-amino-acid decarboxylase and dopamine beta-hydroxylase activities was observed. For this reason, the expression of tyrosine hydroxylase mRNA was studied. Tyrosine hydroxylase mRNA was visualized in the whole brain from 13 days of gestation, but the largest increase of the expression was observed in the hypothalamus. These results are discussed in terms of the relative gene expressions of the three enzymes involved in the biosynthesis of catecholamines and phenolamines in nervous tissues.