The pharmacological actions of N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate (SUN 1165), a new antiarrhythmic agent, on the peripheral nervous system and peripheral organs were studied in various laboratory animals in comparison with those of disopyramide and mexiletine, and the following results were obtained. 1. Large doses (50 or 100 mg/kg p.o.) of SUN 1165 as well as mexiletine had little effects on the pilocarpine-induced hypersalivation and the pupil size in mice. At higher concentration (10(-5) g/ml), SUN 1165 had no effects on the various spasmogen acetylcholine (ACh)-, histamine- or BaCl2-induced contractions in the isolated guinea pig ileum, tracheal smooth muscle and urinary bladder. Disopyramide caused mydriasis, inhibited the pilocarpine-induced hypersalivation at antiarrhythmic doses (10-30 mg/kg p.o.), and suppressed ACh-induced contractions in the various organs. 2. SUN 1165, like disopyramide and mexiletine, decreased the contractile amplitude and diastolic tone of the isolated rabbit ileum. SUN 1165 as well as disopyramide had no effect on the intestinal propulsion even at a large dose (100 mg/kg p.o.). Mexiletine inhibited it at antiarrhythmic doses (10-30 mg/kg p.o.). SUN 1165 only at a large dose (100 mg/kg i.d. or p.o.) inhibited volume of pepsin output in the gastric juice in pylorus-ligated rats and caused a damage to the gastric mucosa. 3. SUN 1165, like disopyramide and mexiletine, slightly potentiated the norepinephrine-induced contraction of the rat vas deferens in vitro. Moreover, SUN 1165 as well as disopyramide and mexiletine slightly potentiated the serotonin-induced contraction of the rat isolated fundus.(ABSTRACT TRUNCATED AT 250 WORDS)