Luteinizing hormone-releasing factor and muscarinic agonists act on the same voltage-sensitive K+-current in bullfrog sympathetic neurones.

The effect of bath-applied luteinizing hormone-releasing factor (LHRF) was recorded in voltage-clamped bullfrog lumbar sympathetic neurones. At a holding potential of -- 30 mV, LHRF induced a steady inward (depolarizing) current and reduced membrane conductance; at -- 60 mV LHRF produced negligible inward current and much less conductance change. The effects of LHRF were accompanied by a reduced amplitude of the slow current relaxations following hyperpolarizing and depolarizing commands, without prominent change in their time-course. This suggests a selective depression of the voltage-sensitive outward K+-current which is suppressed by muscarinic agonists.