Abstract
Afferent projections to the ventromedial hypothalamic nucleus (VMH) of a lizard, Gekko gecko, were studied with wheat germ agglutinin conjugated to horseradish peroxidase. Results indicated that the shell and core areas of the VMH are largely innervated by different telencephalic nuclei but similar brain-stem nuclei. The common brainstem projections include the superior raphe, two isthmal populations (the ventral isthmal nucleus and parvocellular isthmal nucleus), and a dorsal thalamic projection from the posteroventral nucleus. Brainstem projections to the shell but not to the core of the VMH arise from the laterodorsal tegmental nucleus. Telencephalic projections to the VMH core originate from the ventrolateral septum, centromedial DVR, lateral amygdala, medial amygdala, interstitial amygdala, and ventral anterior amygdala. Telencephalic projections to the VMH shell come from the ventral pallidum, the anterior septal nucleus, the dorsal septal nucleus, the striatoamygdalar area, and the ventral posterior amygdala. These results, combined with connectional and topological information from other studies in amphibians, reptiles, and mammals, will be used to suggest homologies between a number of limbic areas, including several amygdalar nuclei.