AFFERENT AND EFFERENT CONNECTIONS OF THE VENTROLATERAL TEGMENTAL AREAIN THE RAT

The present study examined the organization of afferent and efferent c onnections of the rat ventrolateral tegmental area (VLTg) by employing the retrograde and anterograde axonal transport of Fluorogold and Pha seolus vulgaris-leucoagglutinin, respectively. Our interest was focuse d on whether the anatomical connections of the VLTg would provide evid ence as to the involvement of this reticular area in audiomotor behavi or. Our retrograde experiments revealed that minor inputs to the VLTg arise in various telencephalic structures, including the cerebral cort ex. Stronger projections originate in the lateral preoptic area, the z ona incerta, the nucleus of the posterior commissure and some other th alamic areas, the lateral substantia nigra, the deep layers of the sup erior colliculus, the dorsal and lateral central gray, the deep mesenc ephalic nucleus, the paralemniscal zone, the intercollicular nucleus, the external cortex of the inferior colliculus, the oral and caudal po ntine reticular nucleus, the deep cerebellar nuclei, the gigantocellul ar and lateral paragigantocellular reticular nuclei, the prepositus hy poglossal nucleus, the spinal trigeminal nuclei, and the intermediate layers of the spinal cord. Most importantly, we disclosed strong audit ory afferents arising in the dorsal and ventral cochlear nuclei and in the cochlear root nucleus. The efferent projections of the VLTg were found to be less widespread. Telencephalic structures do not receive a ny input from the VLTg. Moderate projections were seen to diencephalic reticular areas, the zona incerta, the nucleus of the posterior commi ssure, and to various other thalamic areas. The major VLTg projections terminate in the deep layers of the superior colliculus, the deep mes encephalic nucleus, the intercollicular nucleus and external cortex of the inferior colliculus, the oral and caudal pontine reticular nucleu s, the gigantocellular and lateral paragigantocellular reticular nucle i, and in the medial column of the facial nucleus. From our data, we c onclude that the VLTg might play a role in sensorimotor behavior.