Fast potentiation of glycine receptor channels by intracellular calcium inneurons and transfected cells

Inhibitory glycine receptors (GlyRs) are mainly expressed in the spinal cor d and in the midbrain, where they control motor and sensory pathways. We de scribe here a fast potentiation of GlyR by intracellular Ca2+. This phenome non was observed in rat spinal cord neurons and in transfected human cell l ines. Potentiation develops in <100 ms, is proportional to Ca2+ influx, and is characterized by an increase in GlyR apparent affinity for glycine. Pho sphorylation and G protein pathways appear not to be involved in the potent iation mechanism. Single-channel recordings in cell-attached and excised pa tches, as well as whole-cell data suggest the presence of a diffusible cyto plasmic factor that modulates the GlyR channel gating properties. Ca2+-indu ced potentiation may be important for rapid modulation of glycinergic synap ses.