Figure 7.

The majority of neurons displayed electrophysiological characteristics of endogenous hippocampal GABAergic interneurons. Top, Neurons are classified based on the presence (types I and II) or absence of I_h current (types III, IV, and V). Types I and II are distinguished by AP drop and AP amplitude. Types III and IV are distinguished by the maximum number of APs in response to depolarizing currents. The type V category contains one cell with a large AP half-width recorded from the granule cell layer. A, Type I cells exhibit I_h currents (arrow) and prominent AP drops. B, Type II cells exhibit I_h currents (arrow) and significantly smaller APs compared with other types. This type also exhibits trains of fast APs. C, Type III neurons resemble type I cells, but without I_h currents. D, Type IV neurons exhibit small AP drops and fast-spiking APs without I_h currents. E, Type V neurons are found in the granule cell layer of the dentate gyrus and resemble granule neurons based on AP half-width and small fast afterhyperpolarizations. F, A GIN neuron recorded from the hilus exhibits firing patterns similar to those from ESNP-derived transplants. Calibration is as indicated.