Citalopram influences mGlu7, but not mGlu4 receptors' expression in the rat brain hippocampus and cortex

Earlier studies showed that chronic electroconvulsive shock (ECS) or imipramine treatment induced a sub-sensitivity of group I metabotropic glutamate receptors (mGluRs) in the hippocampus as well as an increase in the receptor protein level in this structure. In the present study, the effects of chronic imipramine (10 mg/kg, 21 days) or citalopram (10 mg/kg, 21 days) treatment on the mGlu4 or mGlu7 receptors' protein levels in the frontal cortex and hippocampus of the rat brain were examined using the Western blot analysis. We also examined the influence of these drugs' administration on forskolin-stimulated cAMP formation. A non-selective agonist of all receptors belonging to the III group of mGluRs, ACPT-1, was used to establish their effects on the cAMP production. It was found that mGluR7-immunoreactivity both in the hippocampus and in the cerebral cortex was decreased after citalopram, but not imipramine treatment. No changes were observed in the mGluR4-immunoreactivity. Prolonged treatment with these two drugs failed to change the action of group III mGluR agonist, ACPT-1, on the forskolin-stimulated cAMP accumulation. Our results suggest that the mGluR7 receptor is influenced by prolonged treatment of the antidepressant drug citalopram in the brain regions that are considered to be implicated in the clinical response to antidepressant therapy whilst the mGlu4 receptor is not.