Dipyrone (Dp), 4-aminoantipyrine (AA), and antipyrine (At) delay liquid gastric
emptying (GE) in rats. We evaluated adrenergic participation in this phenomenon
in a study in male Wistar rats (250-300 g) pretreated subcutaneously with
guanethidine (GUA), 100 mg·kg−1·day−1, or vehicle (V) for
2 days before experimental treatments. Other groups of animals were pretreated
intravenously (iv) 15 min before treatment with V, prazosin
(PRA; 1 mg/kg), yohimbine (YOH; 3 mg/kg), or propranolol (PRO; 4 mg/kg), or with
intracerebroventricular (icv) administration of 25 µg PRO or V.
The groups were treated iv with saline or with 240 µmol/kg Dp,
AA, or At. GE was determined 10 min later by measuring the percentage of gastric
retention (%GR) of saline labeled with phenol red 10 min after gavage. %GR
(mean±SE, n=8) indicated that GUA abolished the effect of Dp (GUA
vs V=31.7±1.6 vs 47.1±2.3%) and of At
(33.2±2.3 vs 54.7±3.6%) on GE and significantly reduced the
effect of AA (48.1±3.2 vs 67.2±3.1%). PRA and YOH did not
modify the effect of the drugs. %GR (mean±SE, n=8) indicated that
iv, but not icv, PRO abolished the effect
of Dp (PRO vs V=29.1±1.7 vs 46.9±2.7%) and At
(30.5±1.7 vs 49±3.2%) and significantly reduced the effect of
AA (48.4±2.6 vs 59.5±3.1%). These data suggest activation of
peripheral β-adrenoceptors in the delayed GE induced by phenylpyrazolone
derivatives.