Mapping of neural pathways that influence diaphragm activity and project to the lumbar spinal cord in cats

Abstract

During breathing, the diaphragm and abdominal muscles contract out of phase. However, during other behaviors (including vomiting, postural adjustments, and locomotion) simultaneous contractions are required of the diaphragm and other muscle groups including abdominal muscles. Recent studies in cats using transneuronal tracing techniques showed that in addition to neurons in the respiratory groups, cells in the inferior and lateral vestibular nuclei (VN) and medial pontomedullary reticular formation (MRF) influence diaphragm activity. The goal of the present study was to determine if neurons in these regions have collateralized projections to both diaphragm motoneurons and the lumbar spinal cord. For this purpose, the transneuronal tracer rabies virus was injected into the diaphragm and the monosynaptic retrograde tracer Fluoro-Gold (FG) was injected into the Th13-L1 spinal segments. A large fraction of MRF and VN neurons (median of 72 and 91%, respectively) that were infected by rabies virus were dual-labeled by FG. These data show that many MRF and VN neurons that influence diaphragm activity also have a projection to the lumbar spinal cord, and thus likely are involved in coordinating behaviors that require synchronized contractions of the diaphragm and other muscle groups.

Stabilizing function of the diaphragm: dynamic MRI and synchronized spirometric assessment

“…Recently, the Values are in mm. central coordination of the diaphragm and abdominal muscles was experimentally verified (28) demonstrating that the activation of the diaphragm and some abdominal muscles is centrally mediated during stabilization of the trunk during respiration and postural activity. Elevated intra-abdominal pressure via contraction of the diaphragm substantially contributes to the stiffness and stability of the spine (10,14,27).…”

“…J Appl Physiol 109: 1064 -1071, 2010. First published August 12, 2010 doi:10.1152/japplphysiol.01216.2009The aim was to describe diaphragmatic behavior during postural limb activities and examine the ventilatory and stabilizing functions of the diaphragm.…”

Pathophysiological and neurochemical mechanisms of postoperative nausea and vomiting

“…The neural circuitry that generates the emetic episode can be conceptualized as a central pattern generator (CPG) – a network of neural connections that produces rhythmic motor patterns. Although the command neurons (Kupfermann and Weiss, 1978) that drive the CPG for emesis are not well defined, many investigators cite the nucleus of the solitary tract (NTS) and specific nuclei in area of the reticular formation, including the respiratory nuclear groups, as important sites for generating emesis (Fukuda et al, 2003; Horn, 2008; Hornby, 2001; Rice et al, 2010; Shintani et al, 2003). Figure 1 shows the neural pathways potentially responsible for triggering vomiting.…”

Pontine reticulospinal projections in the neonatal mouse: Internal organization and axon trajectories

“…Although an exhaustive description of the literature on bulbospinal projections in nonrodent mammals is beyond the scope of this discussion, it is worth noting that the pRS projection has been described in a variety of mammalian species, particularly the opposum (Martin et al, ; Cabana and Martin, ), cat (Nyberg‐Hansen, ; Petras, ; Basbaum and Fields, ; Tohyama et al, ; Holstege et al, ; Hayes and Rustioni, ; Mitani et al, ; Rice et al, ), and nonhuman primates (Carlton et al, ; Sakai et al, ). In general, these studies indicate that asymmetry with ipsilateral predominance of the pRS projection is a conserved feature, although discrepancies regarding laterality also exist in this literature.…”