There are different types of synapses and receptors that regulate fast and slow synaptic currents. This chapter discusses two classes of synapses (e.g., chemical and electrical) and the receptors that populate these synapses including ionotropic receptors, metabotropic receptors, and gap junctions. We discuss the speed with which these receptors mediate or regulate ionic currents with the purpose of supplying the reader with a general idea of current kinetics. In addition, we include technical considerations when measuring fast and slow synaptic currents as well as, in some cases, the physiological relevance of current kinetics (see Chap. 17 for more details regarding ionotropic receptor kinetics).