Chronic treatment with citalopram induces noradrenaline receptor hypoactivity. A microdialysis study

To investigate whether chronic citalopram administration influences the cyclic AMP (cAMP) synthesis in vivo, microdialysis was used to assess citalopram-induced alterations in extracellular concentrations of cAMP in the dorsal hippocampus of freely moving rats. Citalopram administration for 4 weeks (40 mg/kg p.o. daily) did not affect the baseline levels of cAMP but decreased the noradrenaline-induced enhancement of cAMP levels. No change in forskolin-induced enhancement of cAMP levels was observed. Citalopram in situ did not exert any effect on the cAMP levels. These data support the hypothesis that chronic administration of antidepressants alters the function of noradrenergic receptors.