Differential inhibition by baclofen of amino acid release from cerebral cortex slices

Neurotransmitter glutamate: its clinical importance

Excitatory amino acid glutamate has several important functions in the mammalian central nervous system (CNS). This review focuses on the transmitter role of glutamate and discusses anatomical and pharmacological data of clinical neurological relevance. Experimental and clinical conditions which have been associated with altered content, uptake, membrane binding or release of glutamate in the CNS are discussed. Such conditions include, epilepsy, disorders of the basal ganglia, cerebral ischemia, hypoxia, hypoglycemia, metabolic encephalopathies, olivopontocerebellar atrophy and cerebellar ataxias, amino acidopathies, mental and other neurological disorders. With the exception of a few fibre systems, it is very difficult to differentiate between glutamate and aspartate as CNS transmitters. The term glutamate is, thus, used in the sense glutamate and/or aspartate unless specifically stated.

Variation in behavioral response to baclofen: correlation with benzodiazepine binding sites in mouse forebrain

Mice treated with (+/-)baclofen (2 mg/kg i.p.) displayed profound differences to the motor depressant action of this drug. Mice were divided into three groups termed as responders (20%), moderate responders (65%) and nonresponders (15%). No differences were detected in the spontaneous motor activity between the selected groups. When the animal population in the home cages was kept unchanged the different responses to baclofen were reproducible three weeks after selection. A borderline dose of diazepam (1.5 mg/kg) decreased highly significantly motor activity in baclofen responders but failed to do this in nonresponders group. Ex vivo studies with 3H-flunitrazepam (labelling in vivo and binding carried out in vitro) demonstrated that 3H-flunitrazepam binding in mouse forebrain was significantly smaller in baclofen responders than in nonresponders. Further, the apparent number of 3H-flunitrazepam binding sites in vitro was significantly decreased in the forebrain of baclofen responders. It is concluded that some actions of baclofen depend on the functional state of benzodiazepine recognition sites.