[Ascending and descending projections of posterior hypothalamus neurons immunoreactive to serotonin after administration of 5-hydroxytryptophan in cats].

Through combined retrograde labeling with HRP and serotonin immunohistochemistry, we have demonstrated that ventral and caudal hypothalamic neurons, both non-immunoreactive and immunoreactive to serotonin after administration of 5-hydroxytryptophane, give rise to direct ascending projections to the entire cerebral cortex as well as direct descending projections to the nucleus locus coeruleus alpha in the pontine tegmentum. A retrograde double labeling method with fluorescent dyes further suggested that the population of ascending hypothalamic neurons is different from that of descending ones.