Novelty-induced increase in dopamine release in the rat prefrontal cortex in vivo: inhibition by diazepam.

The effects of graded stressful conditions on extracellular concentrations of dopamine (DA) in the medial prefrontal cortex of rats were measured in vivo using microdialysis. Picking up the rat twice with a 20-min interval increased extracellular DA to 120%, exposure to a novel environment by placement in a clean cage for 20 min to 150% and holding the rat in the hands for 20 min to over 200%. Diazepam (5 mg/kg) decreased DA to about 75% and attenuated the novelty- and handling-induced increases. Exposure to novelty or handling are easy and simple methods to obtain graded increases of in vivo cortical DA release.