Figure 4: The prepulse train protocol was employed to examine the γ-amino-butyric acid (GABA) release from presynaptic terminals of inhibitory interneurons. Different numbers of prepulses (0–320) were applied at 200 Hz to activate GABA release. The relationships between number of prepulses and population spike amplitudes of dementia model mice (SAM-P8, ) and control mice (SAM-R1, ) in the absence and presence of sevoflurane (3.0 vol%) or thiopental (10−5 mol/L) are shown. Inset. The prepulse train protocol initially enhances release of GABA from presynaptic terminals (phase I: reduction in the test-pulse amplitude) and then induces a depletion of neurotransmitter (phase II: disinhibition of the amplitude).