Abstract
Microdialysis is a method designed to directly monitor and evaluate tissue and organ chemistry; it can be used in both preclinical and clinical research. Extracellular molecules diffuse through the membrane into the perfusate solution and, after analysis, they return to tissue.
The perfusate composition then reflects the composition of extracellular fluid. There is no disruption of tissue conditions and body fluid volume, the animals are conscious and move freely during experiments.
Results are largely dependent on the choice of the proper type of the microdialysis probe and analytical method. In experimental pain research, there are three levels of use of microdialysis peripheral tissue, spinal cord, and brain.
It is possible to investigate the algogenic mediators themselves in pain models or their changes in nociception. An ability to examine the selective action of drugs directly at the site of investigation is definitely an advantage.
In peripheral tissue, the role of adenosine in nociception and importance of nitric oxide (NO) as a necessary compound of glutamate and PGE2 action was evaluated. In the spinal cord, studies were conducted to examine central cholinergic neurotransmission, neuropeptides and, most importantly, the action of excitatory and inhibitory amino acids in nociception.
At supraspinal level, similar studies are being performed, with distinct emphasis focused at exploring the associations among glutamate excitatory transmission, GABA-ergic system and endogenous opioids and, also, interactions with the monoarninergic system.