Fig. 11.

Model connectivity diagram and manipulations. Our model of the respiratory and sympathetic circuitry includes structures in the pons, the ventral respiratory column (VRC), the retrotrapezoid nucleus (RTN), and the parafacial respiratory group (pFRG). Orange circles and blue circles, respectively, represent excitatory and inhibitory neuronal populations. Solid green triangles represent sources of tonic drive. Orange and blue solid arrows, respectively, represent excitatory and inhibitory synaptic projections; solid green arrows indicate the distribution of tonic drive. The details of tonic drive distribution [e.g., from drive RTN, drive Pons, and drive ventrolateral medulla (VLM)] can be found in Table 1. Brown circles indicate motoneuron output. The included neural populations are the early inspiratory [early-I (1)] and preinspiratory/inspiratory (pre-I/I) populations of the pre-Bötzinger complex (pre-BötC), the inhibitory postinspiratory (post-I), excitatory postinspiratory [post-I (e)], and the augmenting expiratory (aug-E) populations of the BötC, the ramping inspiratory (ramp-I) and early inspiratory [early-I (2)] populations of the rostral ventral respiratory group (rVRG), the inspiratory-expiratory phase spanning (IE) population of the pons, the late expiratory (late-E) population of the pFRG, and the presympathetic population of the rostral VLM (RVLM). We have implemented experimental manipulations in the model by updating certain model parameters. For example, the galf-filled green triangle indicates a source of tonic drive that is impaired to reproduce saporin-substance P conjugate (SSP-SAP) lesion experiments. Projections that have been removed to simulate glutamatergic blockade are indicated as a dashed line. AbN, abdominal nerve activity; CPG, central pattern generator; cVN, central vagus nerve activity; HN, hypoglossal nerve activity; Kyn, kynurenic acid; PN, phrenic nerve activity; tSN, thoracic sympathetic nerve activity.