The Effects of Anticholinesterase Drugs on Bethanechol- nduced Contractile Responses in Rat Ileum Smooth Muscle

At present, anticholinesterase drugs are valuable as therapeutic agents when cholinergic activity decreased in cases such as glokom, myastenia gravis and postoperative period which induces atony in bladder and intestinal smooth muscles. In these conditions anticholinesterases are expected to increase the levels of acetylcholine by inhibiting the enzyme acetylcholinesterase, thus they can exhibit both muscarinic and nicotinic effects indirectly rather than constituting a direct effect on muscarinic receptors. But recently, it has been shown that anticholinesterase drugs may exhibit a dose-dependent antimuscarinic effect by interacting with muscarinic receptors directly. According to these results, we investigated the dose-dependent effects of anticholinesterases on bethanechol-induced contractile responses at ileum smooth muscle preparations. Our results show that none of the three anticholinesterases did cause any potentialization on contractile responses for bethanechol at their first three concentrations (p > 0,05; paired samples t test). But at their highest concentration such as 1000 M, neostigmine, edrophonium and piridostigmine attenuated the bethanechol induced contractile responses (p 0,05; paired samples t test). These results suggest that anticholinesterases do not have dual effects on bethanechol induced contractile responses in rat ileum smooth muscle preparations. Larger doses of anticholinesterases may evoke antimuscarinic effects on ileum smooth muscle contractions.