VIP-LIKE IMMUNOREACTIVE PROJECTIONS FROM THE DORSAL RAPHE AND CAUDAL LINEAR RAPHE NUCLEI TO THE BED NUCLEUS OF THE STRIA TERMINALIS DEMONSTRATED BY A DOUBLE IMMUNOHISTOCHEMICAL METHOD IN THE RAT

To localize the vasoactive intestinal polypeptide (VIP)-like immunorea ctive neurons at the origin of the plexuses of VIP-immunoreactive fibe rs found in the bed nucleus of the stria terminalis (BNST), we combine d iontophoretic injections of the retrograde tracer cholera toxin B-su bunit (CTb) with VIP immunocytochemistry. Following CTb injections in the BNST, 2 groups of retrogradely labeled neurons immunoreactive to V IP were detected: (1) a dorso-caudal group localized in the dorsal par t of the dorsal raphe nucleus and the adjacent ventro-lateral part of the periaqueductal gray; and (2) a rostral group in the caudal linear raphe nucleus. No double-labeled cells were observed in other nuclei i ncluding those of the amygdala and the supramammillary nucleus.