Brain microdialysis has become a well established and a widely-used technique for in vivo measurement of extracellular levels of neurotransmitters. However, a single neurotransmitter in the perfusates has been measured in most studies. The present paper describes a simultaneous measurement of serotonin and dopamine release in the prefrontal cortex of mice. Using this technique, we examined the modulation by serotonin(1A) receptors of serotonin, dopamine, and noradrenaline release in the cortex of isolation-reared mice. The isolation-reared mouse is a useful model of complicated mood disorders including phenotypes of anxiety, depression, and aggression. The study shows that isolation rearing selectively decreases the sensitivity of serotonin(1A) receptors to increase dopamine release.