Neurochemical evidence for tryptaminergic ascending and descending pathways in the spinal cord of the dog.

The brain and spinal cord of the chronic spinal dog contained higher levels of tryptamine than comparable regions of the intact dog. The most significant brain elevations were found in the cerebellum and mesencephalon. Further, tryptamine in the white matter of the spinal cord above the level of transection was higher than below. These findings have been interpreted as indicating that there are tryptaminergic pathways descending in the white matter of the spinal cord from the mesencephalon, cerebellum and rostral spinal cord. The level of tryptamine below the transection was not different from that found in the intact dog, suggesting that there are not only descending but ascending tryptaminergic pathways and that when the axons are transected. tryptamine accumulates proximal to the level of transection.