Stereoselectivity of spinal neurotransmission: Effects of baclofen enantiomers on tail-flick reflex in rats

Summary Spinal rats and rats with an intact neuraxis received an intrathecal injection of an enantiomer of baclofen. TheR-enantiomer was 100–1000 times more potent than its antipode in inhibiting the tail-flick reflex, both in intact rats and in spinal rats. Spinalization enhanced the inhibitory effects of both enantiomers without altering their dose-response relations. The findings show that baclofen enantiomers have direct actions on stereoselective spinal mechanisms and that spinalization fails to alter the stereoselectivity of spinal mechanisms towards the enantiomers.