DIVERSITY OF SINGLE POTASSIUM CHANNELS IN ISOLATED SNAIL NEURONS

COMPARISON Of K+ channels in mollusk and mammalian neurons has been ma de to elucidate their fundamental properties. Using patch clamp cell-a ttached configuration, K+ channels in isolated snail neurons were sepa rated into three subtypes: with big (BKC), medium (MKC) and small (SKC ) unitary conductances. BKC and MKC were activated at -30 mV and SKC a t more negative potentials. BKC and MKC proved sensitive to TEA, where as SKC were sensitive to 4-AP. Cd2+ in the pipet decreased unitary con ductance of BKC by 55% and of MKC by about 31%. Bath application of 5- T selectively suppressed MKC. It is suggested that BKC can be referred to large conductance Ca2+-dependent K+ currents (KCa), MKC to interme diate conductance KCa and SKC channels comply with the characteristics of A current of mammals. These data show that KCa and A currents may be the most general types of currents generated by K+ channels. (C) 19 98 Rapid Science Ltd.