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J F Coulon

Publications and source records attributed to J F Coulon.

12 recordsLinked to original sources
PubMed1993

Comparative study of biochemical parameters and kinetic properties of dopamine-beta-hydroxylase activity from cat and rat adrenals.

The specific adrenal dopamine-beta-hydroxylase activity measured in cat and rat was: (1) two times higher in cat than in rat; (2) significantly enhanced by ascorbate (up to 5 mM) that acts as a major activator; (3) differently affected by exogenous copper added to the incubation medium, leading to a decrease with large concentrations; and (4) similar, according to the kinetic parameters, thereby demonstrating a greater affinity for ascorbate than for tyramine.

Adrenal Glands↗
PubMed1990

Gene expression of tyrosine hydroxylase in the developing fetal brain.

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.

Actins↗
PubMed1989

Effects of aging on p- and m-octopamine, catecholamines, and their metabolizing enzymes in the rat.

Functions of octopamine in the mammalian brain are still not well known. An important aspect of this problem is the relationship between octopamines and catecholamines. Previous data have shown that their respective ontogenic evolutions are not parallel. Do the changes in brain related to aging also differentially affect these two groups of molecules? In order to check this point, the brain levels of p- and m-octopamine, p-tyramine, noradrenaline, and dopamine, as well as the activities of metabolizing enzymes, were determined in young adult and aging rats (20-26 months). Unlike catecholamines, there is a drastic decrease of p-octopamine after 20 months of age in the hypothalamus and telencephalon. p-Tyramine levels are also lowered. This change appears to be due to a decrease of the aromatic L-amino acid decarboxylase activity. These data, as those of ontogenic studies, confirm that p-octopamine and catecholamine metabolisms may have some independent steps and, moreover, that p-octopamine may have a role in the normal activity of the brain.

2-Hydroxyphenethylamine↗
PubMed1989

Prenatal ontogenesis of brain phenolamines and catecholamines in relation to their metabolizing enzymes in Roman avoider strains of rats.

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.

2-Hydroxyphenethylamine↗
PubMed1987

Effects of triethyltin on brain octopamines and their metabolism in the rat.

The effects of triethyltin given acutely on the cerebral level of p- and m-octopamines were studied in rats. These octopamines were reduced drastically in hypothalamus and brainstem, while noradrenaline and dopamine were only slightly decreased. No important changes were observed in the activities of tyrosine hydroxylase, dopamine beta-hydroxylase or monoamine oxidase. However, the activity of aromatic L-amino acid decarboxylase was significantly reduced. The addition of the inhibitor of dopa decarboxylase, Ro 44602, caused a total inhibition of this enzyme activity. These results are discussed in terms of the possible use of the triethyltin-induced cerebral oedema as a model for the study of some aspects of the phenolamine changes related to cerebral oedema processes.

Animals↗
PubMed1986

High sensitivity of brain octopamine levels to stress.

Rats were submitted to unsignalled and uncontrolled electrical shocks. When re-exposed to the same situation but not shocked, 24 h later, their locomotor activity was significantly reduced compared to that of controls. This conditioned suppression was associated with a significant decrease in p-octopamine (OA) in brain stem and hypothalamus. Shocks delivered just before brain fixation produced an even larger decrease in cerebral OA. Heart levels of OA were not affected. Cerebral and peripheral levels of dopamine and noradrenaline were not significantly or reliably affected. These results, as those of previous experiments, suggest that octopamine is involved in emotional, neurovegetative responses to stress.

Animals↗
PubMed1984

Prenatal ontogenesis of p-, m-octopamine and phenylethanolamine in relation to catecholamines and their metabolizing enzymes in the developing rat brain and heart.

Non-catecholamines such as phenylethanolamine and p-octopamine are present in many invertebrate nervous systems, sometimes in large amounts. These amines are normally present in the rat brain at much lower levels, p- and m-octopamine are present at trace levels in the mammalian brain. The prenatal development of these amines was studied in comparison with those of noradrenaline and dopamine. The activities of tyrosine hydroxylase, dopa decarboxylase, dopamine beta-hydroxylase and monoamine oxidase were determined in parallel. Phenylethanolamine and p-octopamine are more abundant in the brain between 13 and 17 fetal days than dopamine and noradrenaline but decrease after 17 days whereas the levels of m-octopamine and the two catecholamines increase afterwards. Dopa decarboxylase, dopamine beta-hydroxylase and tyrosine hydroxylase are detected early in fetal life (13, 15 and 14.5 days respectively) but monoamine oxidase activity was not found before 18 days.

2-Hydroxyphenethylamine↗
PubMed1984

In vitro occurrence of m-octopamine in the cultured cephalic ganglion of Locusta migratoria L. after L-dopa administration.

Cephalic ganglia of the locust Locusta migratoria L. were cultured in the presence of L-DOPA and inhibitors of dopa decarboxylase or dopamine beta hydroxylase. The addition of L-DOPA to the culture medium resulted in a marked increase of m-octopamine, following higher levels of dopamine. L-DOPA produced an increase of m-tyramine. RO 44602 considerably reduced the levels of p and m-octopamines, m-tyramine, dopamine and noradrenaline while fusaric acid reduced only those of p and m-octopamines, m-tyramine and noradrenaline. Though not normally found in the locust nervous system, m-octopamine appears to be closely related to catecholamines and to be produced via their biosynthesizing enzymes through a hypothetical dehydroxylation step.

Animals↗
PubMed1983

Brain octopamine and strain differences in avoidance behavior.

According to recent research, a significant relationship seems to exist between brain contents of p-octopamine and two-way avoidance responding in rats. Levels of this amine in hypothalamus and brainstem are higher in rats from the Roman High Avoidance (RHA) strain than in rats from the Roman Low Avoidance (RLA) strain. Intracerebroventricular administration of p-octopamine facilitates avoidance responding. The present paper reports the behavioral and neurochemical effects of p-octopamine administration on rats from the Roman strains. This treatment has no significant effect on cerebral levels of catecholamines, but it temporarily suppresses the strain differences in p-octopamine levels. In parallel, it also suppresses the strain differences in two-way avoidance conditioning, its facilitatory effect being much greater in RLA than in RHA rats. Avoidance behavior appears to be a useful model for the study of octopamine functions in the mammalian brain.

Animals↗
PubMed1982

Behavioural and neurochemical effects of intracerebroventricular administrations of p-octopamine in rats.

Intracerebroventricular administration of p-octopamine (250 micrograms) had opposite effects on locomotor activity of rats depending on whether or not the animals were submitted to electric shocks in the experimental situation. When rats were not shocked, their locomotor activity was significantly decreased by the injection. On the other hand, when rats were trained in a shuttle-box, administration of p-octopamine significantly increased avoidance responding and intertrial crossings. The neurochemical effects of the injections were relatively specific: they significantly increased p-octopamine levels in hypothalamus and brainstem but little effect was observed on noradrenaline and dopamine brain contents. These data suggest that octopamine may play the role of a neuromodulator in the central nervous system of mammals.

Animals↗
PubMed1979

Octopamine levels during the moult cycle and adult development in the migratory locust, Locusta migratoria.

Octopamine content of the head of the locust Locusta migratoria has been determined during the last larval stage, moulting and adult life of 3 groups of insects: female and male gregarious, solitary and CO2 solitarized. An important difference was found between these 3 groups. Octopamine contents increased in the middle of the larval life and during the adult life. The moulting time is characterized by a sharp decrease of the octopamine content which becomes identical in the 3 groups of insects. The relation between octopamine content, hormone cycles and motility is discussed.

Animals↗