Figure 2.

Biphasic shape of sigh bursts requires inhibitory synaptic input. A−C, In vitro recordings of sigh and eupnea activities in control conditions and after blockade of glycinergic synapses. A, Integrated traces of preBötC recordings in control conditions (black, top) and in the presence of 1 µM strychnine (blue, bottom). Both recordings show two types of bursts corresponding to eupnea and sigh. B, Sequential slots of the amplitude (in arbitrary units) of inspiratory bursts versus time in control conditions (top) and under strychnine (bottom). Note that the amplitudes of both types of burst were significantly larger in the presence of strychnine. C, Averaged traces for eupneic bursts (n = 10; left) and sigh bursts (n = 8; right) in control (black) and strychnine (blue) conditions. D, In silico average voltage output of a two-compartment coupled model with (top trace) and without (bottom trace) synaptic inhibition ($g_{sy{n}_{INH}}$). E, Average profile of eupnea (left) and sigh bursts (right) obtained from traces in D. Orange stars indicate sigh events.