Differential influences of different stressors upon midbrain raphe neurons in rats.

Various types of stressors were given to different groups of animals to examine their effects on the mesostriatal and mesolimbic serotonergic pathways. Results indicate that shock-induced fighting experience preferentially decreased serotonin (5-HT) levels in the dorsal raphe and striatum, while air puff stimulation selectively lowered 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) contents in the median raphe and hippocampus. Both immobilization and light footshock stress have a more consistent effect on both serotonergic systems. These results suggest that different stressors have differential influences upon central 5-HT neurons and, other than anatomical differentiation, these serotonergic neurons are not homogeneous with respect to their responses to stress either.