There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
The crude extract of magnolia bark, an herbal drug, inhibited the secretion of catecholamines
from bovine adrenal chromaffin cells stimulated by acetylcholine (ACh) in a concentration-dependent
manner (200-900 microg/mL). The extract also diminished the secretion induced by high
K(+), which is a stimulus directly depolarizing the plasma membranes, but its inhibition
was weaker than that of ACh-evoked secretion. beta-Eudesmol, honokiol, magnolol, and
bornyl acetate, but not alpha- and beta-pinenes, all of which are ingredients of magnolia
bark, greatly reduced ACh-evoked secretion. beta-Eudesmol and magnolol also inhibited
high K(+)-induced secretion to an extent similar to that of ACh-evoked secretion.
However, honokiol and bornyl acetate inhibited the secretion induced by high K(+)
much less than the secretion evoked by ACh. ACh-induced Na(+) influx and ACh- or high
K(+)-induced Ca(2+) influx into the cells were diminished by beta-eudesmol or honokiol.
These results indicate that magnolia bark contains some effective components inhibiting
the secretion of catecholamines from bovine adrenal chromaffin cells stimulated by
ACh due to the antagonism of Na(+) and Ca(2+) influxes into the cells. However, inhibition
by the extract of magnolia bark seems to be attributable to honokiol and bornyl acetate.
Furthermore, the results indicate that the inhibitory effect of magnolia bark may
be associated with its pharmacological effect on activities of the nervous system.