Fig. 10. Schematic diagram of differential caudal NTS connections with ventrolateral medulla.

The diagrams provide a synopsis of the differing patterns of innervation of the ventrolateral medulla suggested by the present report in concert with other reports that have examined this question (see Discussion). Arrows at the end of the schematic axons indicate likely excitatory terminations. Triangles at the end of axons indicate inhibitory projections (A).

In A: the output of the lateral, caudal NTS is depicted (blue axons). This projection pattern is typified by 2^nd order NTS neurons for slowly adapting pulmonary stretch receptors (Ezure et al., 2002). These neurons are mostly GABAergic, and, in the rat, are mainly located medially within SolIdf (Ezure and Tanaka, 2004; Takakura et al., 2007). B: illustrates the relatively selective projections from SolC and from caudal SolM (red axons) to rVRG and cVRG as well as to RTN, but not to the intervening BötC and preBötC. C: depicts projections from the lateral part of caudal NTS to ventrolateral medulla (green axons). This is typified by the projections from SolDL and from SolIM that project widely throughout the ventrolateral medulla with the exception that SolDL does not project to RVL. D: shows projections from the area postrema (red axons). Overall these are very similar to the projections originating from SolC and caudal SolM. Significant area postrema projections appear to target the RTN/RVL area as well as the region of rVRG/CVL. In contrast, no area postrema projections are seen to BötC and preBötC compartments of the VRC.