Efferent projections from the lateral hypothalamus in the guinea pig: an autoradiographic study.

Autoradiography was employed to investigate the efferent projections from the lateral hypothalamus in the guinea pig. Lateral hypothalamic axons were traced along the medial forebrain bundle in both ascending and descending directions. Anteriorly, the label was traced along the medial forebrain bundle in both ascending and descending directions. Anteriorly, the label was traced to the lateral preoptic area, diagonal band of Broca, and septal nuclei. Posterior projections included the ventral tegmental area of Tsai, central gray matter and the reticular formation throughout the brain stem. Laterally, the lateral hypothalamic efferents were found in the stria terminalis, amygdala and globus pallidus. Dorsally, the lateral hypothalamic axons projected to the midline nuclei of the thalamus and bilaterally to the lateral habenular nuclei. Projections to the medial hypothalamus included a labeled fiber bundle to the internal layer of the median eminence and to the posterior lobe of the pituitary gland. Labeled fibers and diffuse label were also found in some areas contralateral to the injection site.