Inhibition by arylsulphatase A of Na-independent [3H]-GABA and [3H]-muscimol binding to bovine cerebellar synaptic membranes

Over an identical concentration range, both [³H]-GABA and [³H]-muscimol were bound to bovine cerebellar synaptic membranes through a sodium-independent and high-affinity process. Preincubating the synaptic membrane suspensions with arylsulphatase A inhibited [³H]-GABA and [³H]-muscimol binding. Furthermore, by using 4-nitrocatechol sulphate as a substrate for arylsulphatase A, a direct correlation appeared to exist between the amounts of SO^2?in4 released and the degree of inhibition of [³H]-GABA binding to synaptic membranes. The inhibitory effect of arylsulphatase A was blocked by known inhibitors of arylsulphatase such as AgNO₃. Scatchard analysis of specific [³H]-GABA binding to synaptic membranes showed that arylsulphatase decreased the number of [³H]-GABA binding sites from 2.65 to 1.75 pmol mg proteins without changing appreciably the affinity of [³H]-GABA binding to cerebellar synaptic membranes. These observations are interpreted to indicate that some components of GABA recognition sites may also contain sulpholipid(s) in addition to phospholipid(s).