TETRAHYDROBERBERINE BLOCKS MEMBRANE K-MEDIATED OUTWARD CURRENTS IN ACUTELY DISSOCIATED CA1 NEURONS FROM RAT HIPPOCAMPUS( CHANNELS UNDERLYING ITS INHIBITION OF INTRACELLULAR MESSAGE)

In the patch-clamp perforated whole-cell recording mode, tetrahydrober berine (THB), a novel dopamine (DA) receptor antagonist, inhibits not only DA-induced outward K+ currents, but also acetylcholine-, caffeine -or strychnine-induced outward current. However, THB does not affect e ither GABA-or glycine-induced Cl- currents, or non-NMDA receptor agoni st-induced cation currents. As expected for a K+ channel blocker, THB evokes a downward current deflection accompanied by a decrease of cond uctance. It is concluded that the direct blockade of membrane K+ chann els by THB underlies its inhibition of intracellular message-mediated outward currents. (C) 1997 Elsevier Science B.V.