CGP 35348, a new GABAB antagonist, prevents antinociception and muscle‐relaxant effect induced by baclofen

Abstract

1 CGP 35348, a new GABA_B antagonist, was examined on antinociception induced by (±)-baclofen by use of the hot plate and writhing tests in mice and the paw pressure test in rats. CGP 35348 was also studied in mice on (±)-baclofen-induced impairment of rota-rod performance. 2 CGP 35348, injected either i.p. (60–100 mg kg⁻¹ in mouse) or intracerebroventricularly (i.c.v.) (0.5–2.5 μg per mouse; 25 μg per rat) prevented (±)-baclofen-induced antinociception. 3 CGP 35348 did not modify oxotremorine- and morphine-induced antinociception in mice and rats. 4 CGP 35348 (2.5 μg i.c.v. per mouse) also prevented (±)-baclofen-induced impairment of the rota-rod test. 5 Two other GABA_B antagonists, phaclofen (50 μg i.c.v. per mouse) and 2-OH-saclofen (2.5 μg-10 μg i.c.v. per mouse) did not modify (±)-baclofen-induced antinociception. 7 These results suggest that, at present, CGP 35348 is the only compound able to antagonize (±)-baclofen-induced antinociception.