Sites of origin of gonadotropin releasing hormone containing projections to the amygdala and the interpeduncular nucleus.

The sites of origin of gonadotropin releasing hormone (GnRH) containing projections to the amygdala and the interpeduncular nucleus were studied with immunofluorescence for GnRH in combination with retrograde transport of True blue. After small injections of True blue into the amygdala, retrogradely labeled GnRH producing neurons were identified in the rostral medial septum, the caudal roots of the nervus terminalis, diagonal band, nucleus triangularis septi, nucleus interstitialis striae terminalis, and in the ventrolateral hypothalamus. After injection of True blue into the interpeduncular nucleus, a small GnRH producing cell group in the ventromedial diagonal band, and certain GnRH-positive neurons in the ventral hypothalamus had retrogradely transported the dye. The results suggest a link between the amygdala and the nervus terminalis which is provided in part by GnRH-containing projections. The heterogeneity of the sites of origin of inputs to the amygdala and the interpeduncular nucleus indicates that the 'behavioral' component of the GnRH system is not restricted to a single brain nucleus, but it may be part of a diffuse network which has close anatomical ties with the 'endocrine' GnRH system.