There is evidence for participation of peripheral beta-adrenoceptors in delayed liquid gastric emptying (GE) induced in rats by dipyrone (Dp), 4-aminoantipyrine (AA), and antipyrine (At). The present study aimed to determine whether beta-adrenoceptors are involved in delayed GE induced by phenylpyrazole derivatives and the role of the prevertebral sympathetic nervous system in this condition. Male Wistar rats weighing 220-280 g were used in the study. In the first experiment rats were intravenously pretreated with vehicle (V), atenolol 30 mg/kg (ATE, beta(1)-adrenergic antagonist), or butoxamine 25 mg/kg (BUT, beta(2)-adrenergic antagonist). In the second experiment, rats were pretreated with V or SR59230A 2 mg/kg (SRA, beta(3)-adrenergic antagonist). In the third experiment, rats were subjected to surgical resection of the celiac-superior mesenteric ganglion complex or to sham surgery. The groups were intravenously treated with saline (S), 240 mu mol/kg Dp, AA, or At, 15 min after pretreatment with the antagonists or V and nine days after surgery. GE was determined 10 min later by measuring the percentage of gastric retention (% GR) of saline labeled with phenol red 10 min after gavage. The % GR (means +/- SE, n= 6) values indicated that BUT abolished the effect of Dp (BUT+Dp vs V+Dp: 35.0%+/- 5.1% vs 56.4%+/- 2.7%) and At (BUT+At vs V+At: 33.5%+/- 4.7% vs 52.9%+/- 2.6%) on GE, and significantly reduced (P<0.05) the effect of AA (BUT+AA vs V+AA: 48.0%+/- 5.0% vs 65.2%+/- 3.8%). ATE, SRA, and sympathectomy did not modify the effects of treatments. These results suggest that beta(2)-adrenoceptor activation occurred in delayed liquid gastric emptying induced by the phenylpyrazole derivatives dipyrone, 4-aminoantipyrine, and antipyrine. Additionally, the released neurotransmitter did not originate in the celiac-superior mesenteric ganglion complex.493Fundo de Apoio ao Ensino, a Pesquisa e Extensao (FAEPEX), Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brasil