1996) used were pretreated for 5-10 min before treating 1.0[micro]g/ml of AJEA, and ACh (0.5 [micro]M) and 5-HT(10 [micro]M) were used as positive control drugs in comparison with the extract-induced distal colonic contractility.
Cumulative concentration-response curve, increasing the concentration AJEA (1 x [10.sup.-12] to 1 x [10.sup.-5] g/ml), was applied using a "single-dose" protocol.
AJEA (1 x [10.sup.-12] to 1 x [10.sup.-5] g/ml), an EtOAc extract of Atracty-lodes japonica, dose-dependently stimulated the spontaneous contractility of DCLM (Fig.
3A, AJEA reproduced a typical pattern of muscle contractility in the DCLM of rats.
To understand the pharmacological mechanism responsible for the stimulatory effects of AJEA on the DCLM contractility, a possible involvement of the muscarinic and/or serotoninergic receptors was investigated using pharmacological strategy.
Regarding in a remarkable difference of contractile patterns produced by AJEA and excitatory neurotransmitters such as ACh and 5-HT (Fig.
We fractionated Atractylodes japonica with MeOH, n-hexane, [CHCl.sub.3], EtOAc and n-BuOH and observed that only AJEA, EtOAc fraction, significantly stimulated the spontaneous contractility of DCLM.
Interestingly, AJEA gradually increased the low frequency contraction with high amplitude in the DCLM of rats, and a maximal contraction of DCLM was observed at around 70 min after treating AJEA.
Regarding in these information, we examined whether AJEA-induced contraction of DCLM was mediated, at least, by activation of the muscarinic receptors and observed that the muscarinic [M.sub.3] receptor-preferring antagonist, 4-DAMP, significantly blocked the AJEA-induced DCLM contractions, but the muscarinic [M.sub.2] receptor-preferring antagonist, methoctramine, abolished only the later phase of contractile response of DCLM to AJEA (Fig.
These cellular events lead us to suppose that activation of serotoninergic receptors also possibly mediates the stimulatory effects of AJEA on the DCLM contractility through enhancing ACh releases.