CE with contactless conductivity detection has been used to determine the glycine neurotransmitter in periaqueductal gray matter (PAG) of rats. The LOD for glycine has been decreased to a value of 0.2 mu M by adding 75% v/v of ACN to the samples and increasing the sample zone introduced to a value of 20% of the overall capillary length. The repeatabilities of the analyte migration times and the zone areas amount to 2.1 and 2.7%, respectively. The optimized CE/contactless conductivity detection method makes it possible to determine the micromolar concentrations of glycine in PAG microdialyzates without the necessity of sample derivatization. It follows from a pharmacological study that a local inflammation initiated by an application of carrageenan increased the glycine concentration in the rat PAG seven times, compared with a control. The glycine level in PAG can be decreased and the pain suppressed by administering paracetamol.