Fig. 2. Dose–response of an expiratory neuron to the γ-aminobutyric acid type A (GABA^A) agonist muscimol at 0 and 1 MAC halothane (A  and B ) and neuronal activity at saturation with the GABA^Aantagonist bicuculline at 0 and 1 MAC (C  and D ). The picoejection response curves are shown as the rate-meter recordings of the neuronal discharge frequency Fⁿ(in hertz). The duration of the picoejection is marked. Only the maximally ejected dose rates are indicated. Note the more pronounced response to muscimol (dotted line = F^con) at similar maximal dose rates at 1 MAC compared with 0 MAC. (Insert ) The bottom trace shows a time-expanded view of (B ). The simultaneously recorded phrenic neurogram (PNG, in arbitrary units [a.u.], top ) identifies the neuron as expiratory. The neuronal raw activity directly appears on the oscilloscope as a train of action potential spikes (N.A., middle ), which is also displayed as the neuronal rate-meter recording in spikes per second or hertz (bottom ).