Activity of the Serotonin System of the Prefrontal Cortex in Rats with High and Low Level of Contextual Fear Generalization

Intracerebral microdialysis studies in rats showed that acquisition of a conditioned fear reaction (combination of conditioned sound signal with pain reinforcement in chamber A) was accompanied by serotonin release in the medial prefrontal cortex, which did not occur in animals of the control group (same procedure but without pain stimulation). The level of serotonin release seen during acquisition of the fear reaction was high in animals demonstrating significant freezing (a measure of fear) in chamber B, not associated with pain reinforcement (high level of contextual fear generalization). Serotonin release in rats with low levels of freezing in chamber B (low contextual fear generalization) was low and did not correlate with freezing in chamber A. These data provide evidence that activation of the serotoninergic input of the medial prefrontal cortex on acquisition of the conditioned reflex fear reaction predicted the level of generalization of the contextual component of this reaction. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.