Comparative analysis of the effects of in vivo electrical stimulation of the frontal cortex and gamma-butyrolactone administration on dopamine and dihydroxyphenyl acetic acid (DOPAC) striatal contents in the rat.
The effects of an in vivo electrical stimulation of the frontal cortex were measured on dopamine (DA) and dihydroxyphenyl acetic acid (DOPAC) contents in the striatum of rats anesthetized with chloral hydrate. Results showed a large decrease in DOPAC and a marked increase in DA content, similar to that obtained when nigrostriatal dopaminergic neuron firing rate is reduced by ?-butyrolactone (GBL) administration. If electrical activation of the corticostriatal glutamatergic neurons increased DA release into the striatum as previously shown in cats, the results of the present experiments actually appeared to be paradoxical. Further studies on [(3)H]DA uptake, tyrosine hydroxylase activity, and measurement of serotonin and 5-hydroxyindole acetic acid after cortical stimulation underline the specificity of changes in DA and DOPAC levels. These data may thus suggest that parallel changes in DA and DOPAC striatal contents can be obtained either by activating DA release by presynaptic mechanisms or by decreasing the firing rate of the nigrostriatal dopaminergic neurons.
Dusticier
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Unité de Neurochimie, Laboratoire de Neurosciences Fonctionnelles, 31, chemin Joseph Aiguier, BP 71, 13402 Marseille Cedex 9, France.
Nieoullon
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