Summary
We have found bulbocapnine to be an effective, apparently competitive inhibitor of dopamine depressor responses in the anesthetized, phenoxybenzamine-treated cat. The duration of action of the compound as a dopaminergic antagonist exceeded 3 hrs after an intravenous dose of 8 mg/kg. In the same preparation, however, bulbocapnine did not at all inhibit the depressor responses to acetylcholine, histamine and isoproterenol, indicating a selectivity of action. Although administration of a high dose of propranolol (2 mg/kg, i.v.) did not alter the response of the alpha-receptor blocked cat to dopamine, the subsequent infusion of bulbocapnine remained effective. These results suggest that dopamine is acting as a blood pressure depressor agent via a unique receptor mechanism.
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Pendleton, R.G., Finlay, E. & Sherman, S. Effect of bulbocapnine as a peripheral dopamine receptor antagonists in the anesthetized cat. Naunyn-Schmiedeberg's Arch. Pharmacol. 289, 171–178 (1975). https://doi.org/10.1007/BF00501304
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DOI: https://doi.org/10.1007/BF00501304