MULTICHANNEL RECORDINGS FROM MEMBRANES WHICH CONTAIN GAP-JUNCTIONS .2. SUBSTATES AND CONDUCTANCE SHIFTS

Substates which can last up to several seconds are found in the 100-pS channel of the earthworm septum, a putative gap junction channel. The conductance of these substates is highly variable from preparation to preparation, and they are found at almost every fraction of the whole channel conductance. Another phenomenon seen in multichannel recordin gs is the ''conductance shift'': here the current passed by several op en channels differs from an integral multiple of the current when only one channel is open. These shifts can be modelled by 1) a resistance in series with the channel or 2) long-lived substates. Each of these m odels fails in particular cases to explain either the magnitude or dir ection of the shifts. It is possible that both effects are simultaneou sly present.