FOREBRAIN PROJECTIONS OF THE ROSTRAL NUCLEUS RAPHE MAGNUS SHOWN BY IONTOPHORETIC APPLICATION OF CHOLERATOXIN-B IN RATS

The nucleus raphe magnus belongs to the thermoafferent system. Followi ng iontophoretic choleratoxin b injections in its rostral part, a subs tantial to large number of anterogradely labeled varicose fibres were observed in the medial and lateral preoptic areas, the bed nucleus, th e substantia innominata, the ventral pallidum, the median preoptic nuc leus, the paraventricular hypothalamic nucleus, the central amygdaloid nucleus and the lateral and dorsal hypothalamic areas. A small to mod erate number were seen in the septal nuclei, the diagonal band, the ma gnocellular preoptic nucleus, the anterior hypothalamic area and the p araventricular and intralaminar thalamic nuclei. After choleratoxin b injections in the preoptic, dorsal and lateral hypothalamic areas, a s ubstantial number of retrogradely labeled serotonin immunonegative neu rones were specifically found in the rostral nucleus raphe magnus. Thu s, non-serotonergic rostral nucleus raphe magnus cells might directly modulate hypothalamic thermointegrative neurones.