Journal of Chemical Neuroanatomy 13 (1997) 1–21 Afferent projections to the rat nuclei raphe magnus, raphe pallidus and reticularis gigantocellularis pars  demonstrated by iontophoretic application of choleratoxin (subunit b) Dirk M. Hermann a,b, *, Pierre-Herve ´ Luppi b , Christelle Peyron b , Peter Hinckel a,c , Michel Jouvet b a Physiologisches Institut , Fachbereich Humanmedizin, Justus -L iebig -Uniersita ¨t , A ulweg 129, 35 392 Giessen, Germany b De ´partment de Me ´decine Expe ´rimentale, CNRS ERS 5645, INSERM U52, 8 a. Rockefeller, 69 373 Lyon, France c Institut fu ¨r M edizinische Psychologie, Z entrum fu ¨r Psychosomatik , Justus -L iebig -Uniersita ¨t , Friedrichstr. 36, 35 392 Giessen, Germany Received 30 September 1996; received in revised form 14 January 1997; accepted 8 April 1997 Abstract The aim of the present study was to identify the specific afferent projections to the rostral and caudal nucleus raphe magnus, the gigantocellular reticular nucleus pars  and the rostral nucleus raphe pallidus. For this purpose, small iontophoretic injections of the sensitive retrograde tracer choleratoxin (subunit b) were made in each of these structures. In agreement with previous retrograde studies, after all injection sites, a substantial to large number of labeled neurons were observed in the dorsal hypothalamic area and dorsolateral and ventrolateral parts of the periaqueductal gray, and a small to moderate number were found in the lateral preoptic area, bed nucleus of the stria terminalis, paraventricular hypothalamic nucleus, central nucleus of the amygdala, lateral hypothalamic area, parafascicular area, parabrachial nuclei, subcoeruleus area and parvocellular reticular nucleus. In addition, depending on the nucleus injected, we observed a variable number of retrogradely labeled cells in other regions. After injections in the rostral nucleus raphe magnus, a large number of labeled cells were seen in the prelimbic, A bbreiations: AA, anterior nucleus of the amygdala; ac, anterior commissure; AHA, anterior hypothalamic area; Amb, ambiguus nucleus; ARH, arcuate hypothalamic nucleus; BST, bed nucleus of the stria terminalis; CeA, central nucleus of the amygdala; CLI, caudal linear nucleus; cp, capsule of the pyramidal tract; Cu, cuneate nucleus; DpMe, deep mesencephalic reticular formation; DTg, dorsal tegmental nucleus; ECu, external cuneate nucleus; f, fornix; FF, fields of Forel; fr, fasciculus retroflexus; g7, genu of the facial nerve; Gi, gigantocellular reticular nucleus; HDB, horizontal limb of the diagonal band; ic, internal capsule; III, oculomotor nucleus; IL, infralimbic cortex; IMLF, interstitial nucleus of the medial longitudinal tract; Ins, insular cortex; IO, inferior olivary nuclei; IP, interpeduncular nucleus; IV, trochlear nucleus; KF, Ko ¨lliker-Fuse nucleus; LC, locus coeruleus; LDT, laterodorsal tegmental nucleus; lfp, pontine longitudinal fasciculus; LHA, lateral hypothalamic area; LHb, lateral habenular nucleus; LPGi, lateral paragigantocellular reticular nucleus; LPO, lateral preoptic area; ll, lateral lemniscus; LRt, lateral medullary reticular nucleus; LS, lateral septal nucleus; LtPr, lateral precentral cortex; MCPO, magnocellular preoptic nucleus; MePr, medial precentral cortex; MeV, mesencephalic trigeminal nucleus; MHb, medial habenular nucleus; ml, medial lemniscus; mlf, medial longitudinal fasciculus; MnPO, median preoptic nucleus; MnR, median raphe nucleus; MoV, trigeminal motor nucleus; mp, mammillary peduncle; MPO, medial preoptic area; MPOC, central part of the medial preoptic nucleus; MS, medial septal nucleus; MVe, medial vestibular nucleus; mt, mammillothalamic tract; NB, Barrington’s nucleus; NRD, dorsal raphe nucleus; NRM, nucleus raphe magnus; NRP, nucleus raphe pallidus; opt, optical tract; ox, optic chiasm; Pa, paraventricular hypothalamic nucleus; PAG, periaqueductal gray; PBG, parabigeminal nucleus; PBL, lateral parabrachial nucleus; Pc, parvocellular reticular nucleus; PeRh, perirhinal cortex; PHA, posterior hypothalamic area; Pir, piriform cortex; PL, prelimbic cortex; Pn, pontine reticular nuclei; PPTg, pedunculopontine tegmental nucleus; PrH, nucleus prepositus hypoglossi; PV, paraventricular thalamic nuclei; pyr, pyramidal tract; RPn, pontine raphe nucleus; RR, retrorubral field; rs, rubrospinal tract; RtTg, reticular tegmental nucleus; SCA, subcoeruleus area; scp, superior cerebellar peduncle; SI, substantia innominata; SNC, compact part of the substantia nigra; SNR, reticular part of the substantia nigra; SO, superior olivary nuclei; Sol, nucleus of the solitary tract; SOpt, supraoptic nucleus; spV, spinal tract of the trigeminal nerve; SpVe, spinal vestibular nucleus; STh, subthalamic nucleus; StHy, septohypothalamic nucleus; SubI, subincertal nucleus; SuM, supramammillary nucleus; tz, trapezoid body; VII, facial nucleus; VIIn, facial nerve; VLL, ventral nucleus of the lateral lemniscus; VMH, ventromedial hypothalamic nucleus; XII, hypoglossal nucleus; xscp, decussation of the superior cerebellar peduncle; ZI, zona incerta. * Corresponding author. Present address: Max-Planck-Institut fu ¨r neurologische Forschung, Abteilung fu ¨r experimentelle Neurologie, Gleueler Str. 50, D-50931 Ko ¨ln, Germany. Tel.: +49 221 4726217; fax: +49 221 4726298; e-mail: hermann@mpin-koeln.mpg.de 0891-0618/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved.