A spinal projection of serotonergic neurons of the locus coeruleus in the cat.

A series of studies were done on adult cats to determine if the serotonergic neurons, reported in the nucleus locus coeruleus of that species, project to the lumbar spinal cord. The animals first were injected with 0.2 microliter of Evans blue into the ventral horn of the lumbar cord. Four days later the animals were perfused and prepared for fluorescence microscopic examination. The presence of Evans blue in both noradrenergic and serotonergic cells of the locus coeruleus was clearly evident in animals in which the injection was confined to the ventral horn area. In cat, the monoamine coerulospinal projection to the ventral horn of the lumbar cord arises from both norepinephrine and serotonin-containing neurons.