Fig. 7. Summary scheme of the effects of 1 minimum alveolar concentration sevoflurane on synaptic transmission to inspiratory premotor neurons in the caudal ventral respiratory group. The neuronal control frequency is depressed ( downward arrow ). This is due to a reduction of overall glutamatergic excitation ( downward arrow ) together with an increase in overall inhibitory input ( upward arrow ). Postsynaptic α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) and N -methyl-d-aspartate (NMDA) receptor responses were not changed (ø), which suggests that presynaptic excitatory drive is diminished ( downward arrow ). The inhibitory mechanisms (see ? ) are also investigated in this issue of Anesthesiology. 11