Analgesic properties of the GABA-mimetic THIP.

The analgesic properties of the muscimol analogue THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) in laboratory animals were compared with those of baclofen, morphine and muscimol. THIP was active orally and parenterally and resembled muscimol qualitatively in its actions. Quantitatively, THIP and baclofen were 2--3 times less potent than morphine and 5--15 times less potent than muscimol. The analgesic effects of THIP, baclofen and muscimol were not reversed by naloxone or bicuculline.