Neuroscience Letters, 35 (1983) 253-258 253 Elsevier Scientific Publishers Ireland Ltd. DIFFERENTIAL INPUT FROM THE AMYGDALOID BODY TO THE VENTROMEDIAL HYPOTHALAMIC NUCLEUS IN THE RAT P.G.M. LUITEN*, T. ONO**, H. NISHIJO and M. FUKUDA Department of Physiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama 930-01 (Japan) and *Department of Behavioural and Neural Physiology, State Univer- sity of Groningen, P.O. Box 14, 9750 AA Haren (The Netherlands) (Received December 18th, 1982; Accepted December 25th, 1982) Key words: amygdala - ventromedial hypothalamus - topographic organization - rat Differential amygdaloid afferents to anterior dorsal, anterior ventral, posterior dorsal and posterior ventral subdivisions of the ventromedial hypothalamic nucleus (VMH) were studied by means of retrograde transport of horseradish peroxidase (HRP). Injections of tracer confined to the VMH subdivi- sions mentioned, and enhancement of tracer uptake and transport were achieved by iontophoretic delivery of an HRP solution containing poly-L-c~-ornithine. It was shown that the medial, central, basolateral, basomedial, lateroposterior and intercalated nuclei of the amygdala constitute afferent input sources to the ventromedial nucleus in a topographic pattern related to the various subdivisions of the VMH. This topographically organized amygdala-VMH projection is discussed against the background of the functional role that both amygdala and VMH play in the control of feeding, apart from various other autonomous functions that both brain centers are known to be concerned with. It is a well-documented phenomenon that both the ventromedial hypothalamic nucleus (VMH) and the amygdaloid body of mammals function as parts of a brain substrate that controls a variety of behaviors including food and water intake, defensive, offensive and other social behaviors. Several lesion and stimulation studies, especially more recent ones, have indicated that different subdivisions of both VMH and amygdala are concerned with different functions. Knowledge on the functional differentiation of the VMH is rather limited, but several reports on lesion and electrical stimulation studies point to different roles of various anterior, posterior, as well as dorsal and ventral, parts in social and feeding behavior [6, 12, 19, 24]. Much more extensive is the literature on amygdaloid functions. In the con- text of this paper it suffices to conclude that, apart from various functions not to be mentioned, different aspects of social behavior [3, 17, 23] or feeding behavior [1, 2, 21, 22, 25] are mediated by different nuclei or areas of the amygdaloid com- plex. In general it is suggested by these authors that the various amygdaloid nuclei ** Author for correspondence. 0304-3940/83/0000-0000/$ 03.00 © 1983 Elsevier Scientific Publishers Ireland Ltd.