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Biomedical subjects

A G Roberge

Publications and source records attributed to A G Roberge.

At least 37 records · Page 2Linked to original sources
PubMed1982

Effects of chlordiazepoxide on acquisition and performance of a go-no go successive discrimination task, and on brain biogenic amines in cats.

1. Normal and chlordiazepoxide (0.4 mg/kg/day, per os) treated cats were trained on a symmetric go-no go successive discrimination task with positive reinforcement. 2. The treatment impaired the acquisition, but not the performance once the task was learned. 3. Serotonin, 5-hydroxyindoleacetic acid and noradrenaline were assayed in 12 brain areas in trained cats, and in normal and treated cats which did not undergo the training. 4. The treatment produced localized changes in the serotonin: 5-hydroxyindoleacetic acid ratio and the noradrenaline level; these effects were modified by the training. 5. The drug induced an acquisition deficit rather than a general behavioral disinhibition, and produced neurochemical effects which were dependent upon the brain area, the treatment duration and the behavioral state.

Animals↗
PubMed1981

Different influences of two types of diets commonly used for rats on a series of parameters related to the metabolism of central serotonin and noradrenaline.

A commercial chow and a semipurified diet fed for 14 days to Sprague-Dawley male rats kept under standardized conditions of temperature, humidity, and light had different effects on a series of parameters related to the metabolism of central serotonin and noradrenaline. Rats fed the commercial chow had (1) a lower serum level of the six neutral amino acids (valine, isoleucine leucine, tyrosine, phenylalanine, and methionine) known to compete with tryptophan for its entry into the brain, (2) a higher ratio of tryptophan to the sum of the six neutral amino acids, (3) a lower ratio of tyrosine to the other five neutral amino acids, (4) a lower ratio of serotonin to 5-hydroxyindoleacetic acid in hypothalamus, (5) a higher tryptophan hydroxylase activity in raphe nuclei, and (6) a higher content of noradrenaline in hypothalamus. It is suggested that chow fed rats had a more active central serotonin metabolism in hypothalamus than rats fed the semipurified diet.

Amino Acids↗
PubMed1980

Monoamine roles in retention and reversal of delayed response in cats.

Two experiments were performed to study the effects of manipulation of central monoamines upon behavior in a delayed response (DR) situation. In the first study, serotonin (5-HT) levels were increased by administration of 5-hydroxy-L-tryptophan (5-HTP) and RO4-4602, a decarboxylase inhibitor, to cats that had overlearned the DR. This intervention had no significant effect upon performance in the 0 sec delay condition, but significantly increase error and non-response scores during delay trials; the effect is specific to an "information holding" demand upon the animal and according to the neurochemical analysis appears to be due to a central effect of 5-HT. In a second experiment, dopamine levels were raised by L-DOPA administration during a reversal of the original DR situation, and the effect of L-DOPA on the evolution of response strategies was observed. All animals developed a position habit that proved impossible to correct but L-DOPA animals developed a significant position habit more quickly than controls, thus suggesting a possible relationship between the neostriatal dopamine accumulation and behavioral plasticity.

5-Hydroxytryptophan↗
PubMed1979

Biochemical properties and kinetic parameters of dihydroxyphenylalanine--5-hydroxytryptophan decarboxylase in brain, liver, and adrenals of cat.

Biochemical properties and kinetic parameters of nonpurified dihydroxyphenylalanine-5-hydroxytryptophan decarboxylase extracted from brain and two peripheral organs, liver and adrenals, were studied in the cat. This study shows that decarboxylase activity in brain is lower than in peripheral organs and that 5-hydroxytryptophan can be decarboxylated without exogenous addition of pyridoxal-5'-phosphate (PLP). However, the addition of PLP substantially increases the enzyme activity. Excess of coenzyme (greater than 60 muM) induces inhibition in adrenals and liver but not in the central nervous system (CNS). The observed inhibition might be related to the presence of a tetrahydroisoquinoline derivative formed in the medium. Differentiation between mechanisms of action of decarboxylase in the CNS and peripheral organs is suggested.

5-Hydroxytryptophan↗
PubMed1978

Effect of metergoline on delayed response in cats and its relation to the metabolism of dopamine and serotonin in neostriatal and mesolimbic neurons.

In cats the effect of Metergoline (Liserdol, Farmitalia) was investigated on the performance of a delayed response task and was related to the associated changes in the concentrations of dopamine, nonadrenaline and serotonin in the brain. Metergoline (14 microgram/kg/day, i.m.) administered during the first 10 days of the training significantly decreased response latencies at delay periods of 0, 3, 9 and 27 sec without significantly affecting the number of errors. Biochemical assays showed that the improved performance correlated with the increased dopamine content of limbic structures and the decreased serotonin content in all brain structures. The concentrations of dopamine in the neostriatum remain unchanged. Response latencies and the number of errors in cats treated with Metergoline were significantly different from those in animals treated with L-DOPA (30 mg/kg/day) probably relfecting the specific biochemical disturbance induced by the two drugs. These results suggest an inhibitory influence of serotoninergic pathways on areas like the meso-limbic system retaining high concentrations of dopamine.

Animals↗