The connections of the peripeduncular area studied by retrograde and anterograde transport in the rat.

Lying just ventral to the medial geniculate nucleus and dorsal to the cerebral peduncle, the peripeduncular area (PPA) seems to be implicated in the expression of several sexual reflexes in rodents. The aim of the present investigation was to establish the organization of the afferent and efferent projections of the rat's PPA in an attempt to provide a neural substrate corresponding to the behavioral observations. Based on both retrograde and anterograde transport methods, our results suggest that the PPA: receives its main afferent projections from the insulotemporal cortex, basal ganglia, ventromedial and posterior hypothalamic nuclei, zona incerta, inferior colliculus, intermediate and deep layers of the superior colliculus, central gray, cuneiform nucleus, laterodorsal tegmental nucleus, and dorsal nucleus of the lateral lemniscus and, projects essentially to the basal ganglia, ventromedial hypothalamic nucleus, central gray, cuneiform and pedunculopontine nuclei, deep layers of the superior colliculus, inferior colliculus, and dorsal and ventral nuclei of the lateral lemniscus. These findings, indicating that the PPA is connected with the auditory, motor, and limbic systems and with nonspecific diencephalic and mesencephalic centers, are in agreement with the notion that in rodents this area might play a role in the female sexual receptivity (as expressed by lordosis display or ultrasound production) or male mounting behavior.