C-FOS EXPRESSION IN THE RAT HYPOTHALAMIC PARAVENTRICULAR NUCLEUS INDUCED BY LICL - DESCENDING PROJECTIONS TO THE DORSAL VAGAL MOTOR NUCLEUS

Anorexia inducing lithium chloride is believed to involve descending p rojections from hypothalamus to preganglionic autonomic output neurons . A multiple-labelling technique has presently been used re analyze th e anatomical projections of lithium chloride sensitive neurons in the hypothalamus. Immunolabeling of c-fos was performed to stain neurons a ctivated after LiCl administration, while neurons projecting toward va gal parasympathetic preganglionic levels were identified by injection of diamidino yellow in the dorsal motor nucleus of the vagus. Perikary a of descending neurons were mainly observed in the ventral and latera l areas of the paraventricular hypothalamic nucleus. In contrast, lith ium chloride activated neurons were observed mainly in the magnocellul ar division of the paraventricular nucleus and supraoptic nucleus. Dou ble-labelled neurons were not observed. These data provide evidence th at lithium chloride sensitive neurons in the paraventricular nucleus a re clearly different from those descending toward preganglionic vagal outflow neurons.