The effect of DOPA on the spinal cord. 2. A pharmacological analysis.

Drugs known to influence noradrenergic transmission were investigated with respect to their action on the effect of DOPA on transmission in the spinal cord. The effect of DOPA may be prevented by inhibition of DOPA decarboxylase and by pretreatment with reserpine, it is enhanced by inhibition of monoamine oxidase and reversed by the adrenergic α-receptor blockers phenoxy-benzamine and chlorpromazine; the β-receptor blocker nethalide does not reverse it. The effect of DOPA is reduced in the chronic spinal preparation. These data show that DOPA acts by liberation of catecholamines (dopamine or noradrenaline) in the spinal cord. It is suggested that DOPA increases the synthesis and liberation of transmitter from the terminals of a descending noradrenergic pathway.

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