Modulation of cyclooxygenase-2 on glycine- and glutamate-induced ion currents in rat periaqueductal gray neurons

Cyclooxygenase (COX) is a key enzyme in the conversion of arachidonic acid to prostaglandins. Two isoforms of COX are known: COX-1 and COX-2. In the present study, the modulatory effect of COX-2 on glycine- and glutamate-induced ion currents in periaqueductal gray (PAG) neurons was investigated using the nystatin-perforated patch clamp method. Continuous application of lipopolysaccharides on PAG neurons resulted in increased glycine-induced ion current and decreased glutamate-induced ion current. In contrast, continuous application of celecoxib, selective COX-2 inhibitor, resulted in decreased glycine-induced ion current and increased glutamate-induced ion current. These results demonstrate that COX-2 modulates neuronal activity of PAG, and it can be suggested that COX-2 participates in the regulation of the descending pain control system in the level of PAG neurons.