This study was attempted to investigate the pharmacological action on blood pressure and heart rate in tile urethane-anesthetized rabbits, making use of bupleuri radix methanol extract (BRME).
BRME, when administered into a ear-vein of rabbit, produced a fall in blood pressure and diminished heart rate.
Dose-response curve by increasing dosage of intravenous BRME was established in changes of blood pressure and heart rate. Accumulation and tachyphylaxis in hypotensive action by BRME were not observed.
Depressor action of BRME was not influenced by pretreatment with chlorisondamine, guanethidine, phentolamine, diphenhydramine, cyproheptadine and propranolol.
This hypotensive response of intravenous BRME was not inhibited by vagotomization and pretreatment of hemicholinium, but weakened markedly by atropine-treatment, and potent- iated significantly by physostigmine.
Intravenous BRME markedly suppressed cardioaccelerating action of isoproterenol, but did not affect action of norepinephrine.
With the above results, it is concluded that depressor action by intravenous BRME is due to the peripheral cholinergic effect(muscarinic action) and BRME also reduces heart rate by inhibition of beta- adrenoceptor.
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