EFFECT OF TETRODOTOXIN AND POTASSIUM INFUSION ON MICRODIALYSIS EXTRACTION FRACTION AND EXTRACELLULAR DOPAMINE IN THE NUCLEUS-ACCUMBENS

The effects of tetrodotoxin (TTX) and K+ perfusion on extracellular DA concentration (DA(ext)) and extraction fraction (also known as relati ve recovery or E(d)) were studied using a method for quantitative micr odialysis under transient conditions. TTX administered through the mic rodialysis probe decreased DA(ext) with no effect on E(d). Perfusion w ith high K+ increased DA(ext), with no initial effect on E(d). However , a decrease in E(d) was observed under prolonged depolarization. Thes e data provide further evidence that E(d) may change over the course o f drug administration. This method of quantitative microdialysis is a reliable means for measuring changes in DA(ext) independently of possi ble changes in microdialysis probe efficiency.