Contribution of noradrenaline-, dopamine- and adrenaline-containing axons to the innervation of different regions of the spinal cord of the cat.

The quantitative distributions of noradrenaline (NA), dopamine (DA) and adrenaline (A) were estimated throughout the grey and white matter at various levels of the cat spinal cord (C5, T3, T10 and L2). NA levels were high at all levels of the cord (about 1000 ng/100 mg protein), being more ventrally placed at the cervical level and tending to be more medially placed at lower thoracic and lumbar levels. DA was found at much lower concentrations than NA (less than 100 ng/100 mg protein) and generally decreased in more caudal segments. There was a mediodorsal distribution throughout the cord. A levels were extremely low throughout the cord (less than 17 ng/100 mg protein), but tended to be higher in the rostral-most segments. Up to 5 days after a total transection at T3, there was accumulation of NA in the white matter regions known to contain catecholamine axon tracts. DA, however, showed a much more restricted accumulation in the white matter. The possibility of whether each catecholamine exists separately as a neurotransmitter in the cat spinal cord is discussed.