Effect of antipyrine on the gastric emptying of liquid in rats

Effects of dipyrone on the digestive tract

Dipyrone (metamizole), acting through its main metabolites 4-methyl-amino-antipyrine and 4-amino-antipyrine, has established analgesic, antipyretic, and spasmolytic pharmacological effects, which are mediated by poorly known mechanisms. In rats, intravenously administered dipyrone delays gastric emptying (GE) of liquids with the participation of capsaicin-sensitive afferent fibers. This effect seems to be mediated by norepinephrine originating from the sympathetic nervous system but not from the superior celiac-mesenteric ganglion complex, which activates β2-adrenoceptors. In rats, in contrast to nonselective non-hormonal anti-inflammatory drugs, dipyrone protects the gastric mucosa attenuating the development of gastric ulcers induced by a number of agents. Clinically, it has been demonstrated that dipyrone is effective in the control of colic-like abdominal pain originating from the biliary and intestinal tracts. Since studies in humans and animals have demonstrated the presence of β2-adrenoceptors in biliary tract smooth muscle and β2-adrenoceptor activation has been shown to occur in dipyrone-induced delayed GE, it is likely that this kind of receptors may participate in the reduction of smooth muscle spasm of the sphincter of Oddi induced by dipyrone. There is no evidence that dipyrone may interfere with small bowel and colon motility, and the clinical results of its therapeutic use in intestinal colic appear to be due to its analgesic effect.

Effect of selective β-adrenoceptor blockade and surgical resection of the celiac-superior mesenteric ganglion complex on delayed liquid gastric emptying induced by dipyrone, 4-aminoantipyrine, and antipyrine in rats

There is evidence for participation of peripheral β-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 β-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, β₁-adrenergic antagonist), or butoxamine 25 mg/kg (BUT, β₂-adrenergic antagonist). In the second experiment, rats were pretreated with V or SR59230A 2 mg/kg (SRA, β₃-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 µmol/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 β₂-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.

Evidence for the involvement of peripheral β-adrenoceptors in delayed liquid gastric emptying induced by dipyrone, 4-aminoantipyrine, and antipyrine in rats

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.

Effect of baclofen on liquid and solid gastric emptying in rats

CONTEXT

Gamma-aminobutyric acid (GABA) is a potent inhibitory neurotransmitter. There is evidence that GABA(B) receptors located in the dorsal complex and in afferent fibers of the vagus nerve participate in the control of gastrointestinal motility.

OBJECTIVE

To assess the intracerebroventricularly (ICV) and intravenously (IV) effect of baclofen, a GABA(B) receptor agonist, on liquid and solid gastric emptying in rats.

METHODS

Adult male Wistar rats weighing 250-300 g (n = 6-8 animals) were used. Gastric emptying of liquid test meals labeled with phenol red was evaluated by the determination of percent gastric retention (%GR) 10 and 15 min after orogastric administration of saline and 10% glucose meals, respectively. Baclofen was injected ICV (1 and 2 µg/animal) through a tube implanted into the lateral ventricle of the brain and was injected IV (1 and 2 mg/kg) into a tail vein. The gastric emptying of liquid was determined 10 or 30 min after ICV and IV baclofen administration, respectively. The gastric emptying of the solid meal was assessed by the determination of percent gastric retention 2 h after the beginning of the ingestion of the habitual ratio by the animal, consumed over a period of 30 min. Baclofen was administered ICV (1 and 2 µg/animal) or IV (1 and 2 mg/kg) immediately after the end of the ingestion of the solid meal. The control groups received vehicle (sterile saline solution) ICV or IV.

RESULTS

The group of animals receiving baclofen ICV (2 mg/animal) presented a significantly lower (P<0.05, Tukey test) %GR (mean ± SEM) of the saline (18.1 ± 2.5%) compared to control (33.2 ± 2.2%). In the group receiving the drug IV, the gastric retention of the same test meal did not differ from control. ICV and IV administration of baclofen had no effect on the gastric emptying of the 10% glucose solution compared to control. ICV administration of 1 or 2 mg baclofen/animal significantly increased the gastric retention of the solid test meal (57.9 ± 6.5% and 66.6 ± 6.3%, respectively) compared to control (35.1 ± 4.4%). The same phenomenon was observed only with the IV dose of 2 mg/kg (71.9 ± 2.6%) compared to control (52.7 ± 2.8%).

CONCLUSION

Baclofen administered: 1. ICV (2 µg/animal), but not IV, increased gastric emptying of a non-caloric isotonic liquid test meal (saline); 2. when administered ICV or IV, it had no effect of gastric emptying of a 10% glucose solution; 3) when administered ICV (1 and 2 mg/animal) and IV (2 mg/kg) it delayed the gastric emptying of the solid meal.

Phenylpyrazolone derivatives inhibit gastric emptying in rats by a capsaicin-sensitive afferent pathway

Dipyrone (Dp), 4-aminoantipyrine (AA) and antipyrine (At) administered iv and Dp administered icv delay gastric emptying (GE) in rats. The participation of capsaicin (Cps)-sensitive afferent fibers in this phenomenon was evaluated. Male Wistar rats were pretreated sc with Cps (50 mg/kg) or vehicle between the first and second day of life and both groups were submitted to the eye-wiping test. GE was determined in these animals at the age of 8/9 weeks (weight: 200-300 g). Ten minutes before the study, the animals of both groups were treated iv with Dp, AA or At (240 micromol/kg), or saline; or treated icv with Dp (4 micromol/animal) or saline. GE was determined 10 min after treatment by measuring % gastric retention (GR) of saline labeled with phenol red 10 min after orogastric administration. Percent GR (mean +/- SEM, N = 8) in animals pretreated with Cps and treated with Dp, AA or At (35.8 +/- 3.2, 35.4 +/- 2.2, and 35.6 +/- 2%, respectively) did not differ from the GR of saline-treated animals pretreated with vehicle (36.8 +/- 2.8%) and was significantly lower than in animals pretreated with vehicle and treated with the drugs (52.1 +/- 2.8, 66.2 +/- 4, and 55.8 +/- 3%, respectively). The effect of icv administration of Dp (N = 6) was not modified by pretreatment with Cps (63.3 +/- 5.7%) compared to Dp-treated animals pretreated with vehicle (62.3 +/- 2.4%). The results suggest the participation of capsaicin-sensitive afferent fibers in the delayed GE induced by iv administration of Dp, AA and At, but not of icv Dp.

Effect of 4-aminoantipyrine on gastric compliance and liquid emptying in rats

Dipyrone (Dp) delays gastric emptying (GE) in rats. There is no information about whether 4-aminoantipyrine (AA), one of its metabolites, has the same effect. The objectives of the present study were to assess the effects of AA and Dp on GE when administered intravenously (iv) and intracerebroventricularly (icv) (240 micromol/kg and 4 micromol/animal, respectively) and on gastric compliance when administered iv (240 micromol/kg). GE was determined in male Wistar rats weighing 250-300 g (5-10 per group) after icv or iv injection of the drug by measuring percent gastric retention (GR) of a saline meal labeled with phenol red 10 min after administration by gavage. Gastric compliance was estimated in anesthetized rats (10-11 per group), with the construction of volume-pressure curves during intragastric infusion of a saline meal. Compliance was significantly greater in animals receiving Dp (mean +/- SEM = 0.26 +/- 0.009 mL/mmHg) and AA (0.24 +/- 0.012 mL/mmHg) than in controls (0.19 +/- 0.009 mL/mmHg). AA and Dp administered iv significantly increased GR (64.4 +/- 2.5 and 54.3 +/- 3.8%, respectively) compared to control (34 +/- 2.2%), a phenomenon observed only with Dp after icv administration. Subdiaphragmatic vagotomy reduced the effect of AA (GR = 31.4 +/- 1.5%) compared to sham-treated animals. Baclofen, a GABAB receptor agonist, administered icv significantly reduced the effect of AA (GR = 28.1 +/- 1.3%). We conclude that Dp and AA increased gastric compliance and AA delayed GE, with the participation of the vagus nerve, through a pathway that does not involve a direct action of the drug on the central nervous system.