Cardiovascular and biochemical effects of L-DOPA in the sea-gull, Larus argentatus.
We have investigated the effects of L-DOPA alone and in combination with three different inhibitors of L-aromatic aminoacid decarboxylase (DC), carbidopa, benserazid and alpha-monofluoromethyldopa (MFMD) on blood pressure (BP) and catecholamine content in conscious or anaesthetized sea-gulls, Larus argentatus. The results show that L-DOPA, given i.p., is taken up and decarboxylated to dopamine (DA) in brain and heart. Carbidopa inhibits the peripheral synthesis of DA from exogenous L-DOPA while central decarboxylation is enhanced when compared to the effects of L-DOPA alone. Benserazid and MFMD inhibit both central and peripheral formation of DA after L-DOPA injections. L-DOPA given alone leads to a slight increase in BP, while heart rate (HR) decreases somewhat. After peripheral inhibition of DC using carbidopa, L-DOPA elicits a reduction in BP both in conscious and anaesthetized birds. HR is significantly reduced in anaesthetized birds. Pretreatment with benserazid or MFMD abolishes the cardiovascular effects of L-DOPA. It is concluded that L-DOPA lowers the BP via activation of central mechanisms.
D000818:Animals; D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D001717:Birds / Q000378:metabolism / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects*; D002395:Catecholamines / Q000032:analysis; D004298:Dopamine / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D007980:Levodopa / Q000494:pharmacology*; D009206:Myocardium / Q000032:analysis
D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D002395:Catecholamines; D007980:Levodopa; D004298:Dopamine