title: Effect of the GABAB agonist baclofen on dipyrone-induced delayed gastric emptying in rats.
abstract: Dipyrone administered intravenously (iv) or intracerebroventricularly (icv) delays gastric emptying (GE) in rats. Gamma-aminobutyric acid (GABA) is the most potent inhibitory neurotransmitter of the central nervous system. The objective of the present study was to determine the effect of icv baclofen, a GABAB receptor agonist, on delayed GE induced by dipyrone. Adult male Wistar rats received a saline test meal containing phenol red as a marker. GE was indirectly evaluated by determining the percent of gastric retention (%GR) of the meal 10 min after orogastric administration. In the first experiment, the animals were injected iv with vehicle (Civ) or 80 mg/kg (240 micromol/kg) dipyrone (Dpiv), followed by icv injection of 10 microl vehicle (bac0), or 0.5 (bac0.5), 1 (bac1) or 2 microg (bac2) baclofen. In the second experiment, the animals were injected icv with 5 microl vehicle (Cicv) or an equal volume of a solution containing 4 micromol (1333.2 microg) dipyrone (Dpicv), followed by 5 microl vehicle (bac0) or 1 microg baclofen (bac1). GE was determined 10 min after icv injection. There was no significant difference between control animals from one experiment to another concerning GR values. Baclofen at the doses of 1 and 2 microg significantly reduced mean %GR induced by iv dipyrone (Dpivbac1 = 35.9% and Dpivbac2 = 26.9% vs Dpivbac0 = 51.8%). Similarly, baclofen significantly reduced the effect of dipyrone injected icv (mean %GR: Dpicvbac1 = 30.4% vs Dpicvbac0 = 54.2%). The present results suggest that dipyrone induces delayed GE through a route in the central nervous system that is blocked by the activation of GABAB receptors.
authors.affiliation: Departamento de Pediatria, Núcleo de Medicina e Cirurgia Experimental and Centro de Investigação em Pediatria, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, SP, Brazil. pediat@fcm.unicamp.br
authors.forename: E F
authors.initials: EF
authors.lastname: Collares
authors.forename: A M
authors.initials: AM
authors.lastname: Vinagre
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001418:Baclofen / Q000494:pharmacology*; D002490:Central Nervous System / Q000187:drug effects; D004177:Dipyrone / Q000494:pharmacology*; D018755:GABA Agonists / Q000494:pharmacology*; D058786:GABA-B Receptor Agonists; D005746:Gastric Emptying / Q000187:drug effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D018755:GABA Agonists; D058786:GABA-B Receptor Agonists; D004177:Dipyrone; D001418:Baclofen