Fig. 7. Summary scheme of the effects of 1 minimum alveolar concentration halothane on synaptic transmission to inspiratory premotor neurons in the caudal ventral respiratory group. The neuronal control frequency (Fcon ) is depressed (downward arrow ). This is due to a reduction of overall glutamatergic drive (downward arrow ). The AMPA and N -methyl-d-aspartate (NMDA) receptor responses are decreased (downward arrow ), whereas presynaptic excitatory drive is not significantly changed (ø). Overall inhibitory drive is not significantly changed by the anesthetic (ø). However, the γ-aminobutyric acid type A (GABAA) receptor response is greatly enhanced (upward arrow ), indicating that presynaptic inhibitory input is depressed by the anesthetic.