AN ANALYSIS OF THE PERIPHERAL EFFECTS OF l‐DOPA ON AUTONOMIC NERVE FUNCTION

Open Access
Publisher Website
Google Scholar
Abstract
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. 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. 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. 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. The degree of lumbar sympathetic chain inhibition correlated with the pressor response following l‐DOPA, and both effects were prevented by prior decarboxylase inhibition. 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.