EFFECT OF THE STEROIDAL ALKALOID BUXAMINOL-E ON BLOOD-PRESSURE, ACETYLCHOLINESTERASE ACTIVITY AND (H-3)QUINUCLIDINYL BENZILATE BINDING IN CEREBRAL-CORTEX

Pharmacological properties of the steroidal alkaloid buxaminol-E isolated from Buxus sempervirens varietas bullata were studied in relation to the cholinergic nervous system. In anaesthetised cats buxaminol-E (1.25-mu-mol/kg) initially induced a small short-lasting increase in blood pressure followed by marked hypotension. Atropine (1.47-mu-mol/kg) inhibited the hypotensive effect almost completely and methylatropine (1.47-mu-mol/kg) partially. Buxaminol-E and the muscarinic agonists McN-A-343 and bethanechol inhibited the binding of the muscarinic antagonist (H-3)quinuclidinyl benzilate in cat and rabbit cerebral cortex membranes in decreasing order of potency. In about 10-fold higher concentrations they also inhibited acetylcholinesterase activity in cat cerebral cortex in the same order of potency. The results suggest that the hypotensive effect of buxaminol-E could be due to both central and peripheral activation of muscarinic receptors, and to a lesser degree to inhibition of acetylcholinesterase activity.