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

Abstract

CGP 35348, a new GABAB 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. 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. CGP 35348 did not modify oxotremorine‐ and morphine‐induced antinociception in mice and rats. CGP 35348 (2.5 μg i.c.v. per mouse) also prevented (±)‐baclofen‐induced impairment of the rota‐rod test. Two other GABAB 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. These results suggest that, at present, CGP 35348 is the only compound able to antagonize (±)‐baclofen‐induced antinociception. 1991 British Pharmacological Society