Tiny guide canulae with a diameter of 0.38 mm were precisely placed in the nucleus accumbens and medial prefrontal cortex using stereostaxic surgery. These canulae accomodate the microdialysis probe on test days. The canulae are cemented in place with dental acrylic. The rat is anesthetized and feels no pain during this procedure, and as the brain lacks pain receptors, they cannot feel the canula implanted their brain upon awakening from the anaesthesia. After habituating the rats so they are comfortable in their dialysis bowls, we use pourous microdialysis probes (diameter of 0.24 mm) to sample the extracellular fluid of the brain every fifteen minutes, giving us a snapshot of the local neurochemical environment in the prefrontal cortex.
To test our research question, we infuse NMDA (Glutamate agonist), CPP (NMDA antagonist), or SCH-23390 (D1 antagonist) into the Nucleus Accumbens. The sample is pumped into a plastic vial and placed in a freezer to ensure no degradation of neurotransmitters. The ensuing changes in ACh release are mirrored in the microdialysis probe sample. When the samples are ready to be analyzed, they are placed in a High Performance Liquid Chromotography machine (HPLC), a sophistocated electrochemical apparatus, that quantifies the amount of ACh released and then feeds these data to the adjacent computer, so the change in ACh release can be graphed over fifteen minute intervals.