Single-channel currents are measured in isolated areas of excitable-cell membranes using the patch electrode method. Stochastic activation of gated ionic channels is studied as an indicator of the molecular conformation changes underlying excitation in the nervous system. Inhibitory postsynaptic channels from mouse spinal cord neurons and electrically activated potassium channels from neuroblastoma and myeloma cells have been the main objects of study. Modification of channel gating by pharmacological agents and neurotransmitters is studied as a means of establishing a picture of synaptic integration based on the properties of membrane ionic channels.