Fig. 1. Synaptic scheme that was used to analyze the effects of halothane on overall synaptic neurotransmission in expiratory VRG neurons (EBSNs) during their active discharge phase in the vagotomized dog. (  Left ) The spontaneous expiratory neuron activity,  F ⁿ, is determined by the strength of excitatory (  F ^e) and inhibitory (  F ⁱ) inputs. (  Right ) The excitatory glutamatergic input  F ^eis modulated by the inhibitory GABA^Areceptor input  F ⁱin a multiplicative fashion that results in an attenuation of the neuron activity by the factor (1 −α), where α is an inhibitory constant that characterizes the strength of the inhibitory input. During complete block of the inhibitory input with bicuculline, α becomes zero. Thus, during complete bicuculline block,  F ⁿreflects the neuronal activity during full transmission of the excitatory input  F ^e, (i.e.,  F ⁿ=  F ^e). Comparing the neuron activities before and during complete bicuculline block at two different levels of anesthesia allows the calculation of the effects of the anesthetic dose increase on overall excitatory and inhibitory neurotransmission (see also  table 1