There are several developing lines of evidence suggesting that brain receptors called GABA-B
receptors play a significant role in addiction and its treatment. The investigators wish to
examine the sensitivity of brain GABA-B receptors in alcohol and opiate addicts as part of
the investigators MRC programme of research in neurotransmitters in alcohol and opiate
addiction (NOAA). In this present study the investigators will give 2 different single doses
of a drug called baclofen, and a placebo, to 8 healthy male volunteers. This drug affects
GABA-B receptors in the central nervous system and is licensed for the treatment of
spasticity in people with eg spinal injuries; the investigators are interested in its effects
on brain GABA-B receptors. The investigators will measure EEG (brainwaves), eye movements,
blood pressure and heart rate, motor co-ordination and subjective effects and also blood
levels of the drug in the investigators volunteers before and at intervals after dosing. The
investigators will use a double-blind randomised design to minimise expectation effects. The
study will provide information on timing and magnitude of effects of baclofen on brain
function in healthy subjects so that the investigators can optimise selection and timing of
functional measures in future studies of addicts.