POSTMORTEM ANTEROGRADE TRACING OF INTRAHYPOTHALAMIC PROJECTIONS OF THE HUMAN DORSOMEDIAL NUCLEUS OF THE HYPOTHALAMUS

Together with the paraventricular nucleus (PVN), the dorsomedial nucle us of the hypothalamus (DMH) acts as one of the hypothalamic centers t hat integrate autonomic and central information. The DMH in the rat br ain has extensive intrahypothalamic connections and is implicated in a wide variety of functions. Up until now, no knowledge has been availa ble to indicate that the human DMH might have functions similar to tho se of the rat DMH. In the present study, intrahypothalamic efferent pr ojections of the human DMH were revealed by a recently developed in vi tro postmortem tracing method. It was found that the most densely inne rvated areas are the PVN, the ventromedial nucleus of the hypothalamus , and the area below the PVN. Other significant terminal fields includ e the periventricular nucleus, the lateral hypothalamic area, and the medial part of the anteroventral hypothalamic area. Scarce fibers proj ect to the suprachiasmatic nucleus, infundibular nucleus, posterior hy pothalamic nucleus, and posterior part of the bed nucleus of the stria terminals. The projections of the ventral and dorsal part of the DMH show some differences. The dorsal part of the DMH has denser projectio ns to the dorsal part of the PVN than to the ventral part of the PVN. In contrast, the ventral part of the DMH has denser projections to the ventral part of the PVN. Labeled fibers in the PVN from ventral and d orsal DMH appear to run near many vasopressin and oxytocin neurons of different sizes, and also near some corticotropin- releasing hormone n eurons, suggesting that the DMH neurons may directly affect the functi oning of these PVN neurons. In many aspects, the observed projections of the human DMH resemble those of the rat, indicating that the organi zation of DMH intrahypothalamic projections of human is similar to tha t of rat. The functional significance of DMH intrahypothalamic connect ions is discussed. (C) 1998 Wiley-Liss, Inc.