ATP ACTIVATES JUNCTIONAL AND EXTRAJUNCTIONAL ACETYLCHOLINE-RECEPTOR CHANNELS IN ISOLATED ADULT-RAT MUSCLE-FIBERS

Single-channel recordings in the cell-attached configuration were made on freshly dissociated and cultured rat muscle fibres. We demonstrate that ATP (50-100-mu-M) elicits single channel currents in freshly isolated fibres. These ATP-activated channels have a slope conductance similar to that determined for ACh-activated channels but exhibit a shorter open time. We also show that ATP activates extrajunctional AChR-channels in the membrane of long-term cultured muscle fibres. Here the ATP activated channel has a slope conductance and open time characteristics similar to those of the ACh-activated channel.