EN
Diclofenac sodium (DS) acts as a potent cyclooxygenase inhibititor, reducing arachidonic acid release and prostaglandins formation. It is commonly used as a non-steroid anti-infl ammatory drug and the potential adverse effects of its administration during pregnancy are of medical and public concern. In the present study, the DS in a dose of 1 mg/kg/day was subcutaneously injected to the pregnant Wistar rats throughout 5–20 gestational days. One group of 4-week old pups was sacrifi ced and the counts of principal neurons in cerebellum and hippocampus were done using stereological methods. Another group of pups was subjected to a battery of behavioral tasks. A signifi cant decrease in the total number of Purkinje cells but not CA pyramidal neurons was observed in the drug-treated juvenile pups. No substantial between-group differences were found in most of the applied behavioral tasks including plus maze anxiety test, and learning/memory tasks such as 12-arm radial maze and the Morris water maze, the latter run both under allo- and idiothetic stimulus conditions. Only in the Open Field test, fetal DS male but not female pups showed slower rate of habituation compared to controls. The obtained results indicated that the moderate doses of DS administered between 5–20 gestation days in rats equivalent of the second half of the 1st and the whole 2nd trimester in human) resulted in some neuronal losses which, however, had no adverse behavioral impact.