Minocycline is a tetracyclic antibiotic whose non-antibacterial activities, including anti-inflammatory, antinociceptive, and neuroprotective effects, have been widely studied. Thus, a better understanding of the mechanisms underlying its pleiotropic activities is important. Primary microglial cell cultures were established from cerebral cortices of 1-day neonatal Wistar rats. Minocycline (3-100 µM) or its vehicle was added to the culture media 30 min prior to 24 h incubation with lipopolysaccharide (LPS; 10 ng/mL). Cell viability after these treatments was assessed by ATP-based luminescence test. Prostaglandin (PG) E(2) and 8-iso-PGF(2α) were determined by enzyme immunoassays. Cyclooxygenase-2 and microsomal PGE(2) synthase-1 protein levels were measured by western blot analysis. First, it was shown that minocycline (30 or 100 µM) inhibits PGE(2) production in LPS-activated primary rat microglial cells. Then, by investigating targets involved in this inhibition, it was found that minocycline (3-100 µM) inhibits microsomal PGE(2) synthase-1, but not cyclooxygenase-2, expression. Additionally, minocycline (3-100 µM) inhibited the production of 8-iso-PGF(2α). This study warrants the conduction of in vivo studies to evaluate the pharmacological relevance of these findings.