1 the ability of intravenous l-dopa to block sympathetic and parsympathetic nerves has been studied in cats and dogs pretreated with a monoamine oxidase inhibitor.2 l-dopa inhibited positive chronotropic and pressor responses to dimethylphenylpiperazinium ( dmpp ) and mcn-a-343 in dogs , and contractions of the nictitating membrane produced by these ganglion stimulants in cats.3 responses of the cat nictitating membrane to preganglionic stimulation were inhibited by l-dopa to a greater extent than those to postganglionic stimulation of the cervical sympathetic chain.4 in dogs , l-dopa had no vagolytic action , but depressed vasoconstrictor responses elicited in the perfused hind-limb by electrical stimulation of the lumbar sympathetic chain.5 the degree of lumbar sympathetic chain inhibition correlated with the pressor response following l-dopa , and both effects were prevented by prior decarboxylase inhibition.6 these results suggest that the decarboxylation products of l-dopa do not impair parasympathetic nerve activity but depress sympathetic nerve function predominantly by inhibiting both muscarinic and nicotinic sites of sympathetic ganglia .
C0013023
dopa
C0023570
l-dopa