Effect of chronic gestational treatment with caffeine or theophylline on Group I metabotropic glutamate receptors in maternal and fetal brain

doi:10.1111/j.1471-4159.2005.03211.x

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Wiley InterScience

Journal of Neurochemistry

Volume 94 Issue 2, Pages 440 - 451

Published Online: 2 Jun 2005

Published for the International Society for Neurochemistry

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Effect of chronic gestational treatment with caffeine or theophylline on Group I metabotropic glutamate receptors in maternal and fetal brain

D. León, J. L. Albasanz, M. A. Ruíz, I. Iglesias and M. Martín

Departamento de Química Inorgánica, Orgánica y Bioquímica, Facultad de Químicas, Centro Regional de Investigaciones Biomédicas, Universidad de Castilla-La Mancha, Ciudad Real, Spain

Address correspondence and reprint requests to Dra Mairena Martín, Área de Bioquímica, Facultad de Ciencias Químicas, Avenida Camilo José Cela 10, 13071, Ciudad Real, Spain.
E-mail: Mairena.Martin@uclm.es

KEYWORDS

desensitization • down-regulation • metabotropic glutamate receptor • pregnancy • rat brain

Abstract

Pregnant rats were treated throughout the gestational period with either caffeine or theophylline, and its effect on the metabotropic glutamate receptor (mGluRs) signal transduction pathway was studied in both maternal and fetal brain. In maternal brain, radioligand binding assays showed that chronic treatment with methylxanthines caused a significant decrease in the total number of mGluRs. This decrease was accompanied by an increase in receptor affinity. Immunodetection showed that mGluR_1a and phospholipase C β₁ (PLCβ₁) were significantly decreased in response to chronic methylxanthine treatment, whereas αG_q/11 was not affected. A loss was also detected of PLC stimulation mediated by (S)-3,5-dihydroxyphenylglycine (DHPG), a selective Group I mGluR agonist, suggesting desensitization of the mGluR/PLC pathway. In fetal brain, a loss in total mGluRs was observed in fetuses from mothers treated with caffeine or theophylline, without variation in receptor affinity. A decrease in mGluR_1a, αG_q/11 and PLCβ₁ levels was also observed in response to treatment. However, changes detected in this immature tissue were not associated with variations in PLC activity. These results suggest that chronic caffeine or theophylline treatment down-regulates several mGluR/PLC transduction pathway components in both maternal and fetal brain, causing a loss of receptor responsiveness only in maternal brain.