Pattern of distribution of serotonergic fibers to the orbitomedial and insular cortex in the rat

► We examined the distribution of serotonergic fibers to the prefrontal cortex in the rat using antisera to the serotonin transporter protein. ► We demonstrated that serotonergic fibers distribute massively to the three divisions of the prefrontal cortex and each of their subdivisions. ► These include the medial, orbital and insular divisions of the prefrontal cortex (PFC). ► By contrast, the serotonergic innervation of sensorimotor regions of the PFC was considerably less pronounced. ► These findings indicate a marked 5-HT influence on the PFC putatively involved in the modulation of affective and cognitive behaviors of the PFC.