|
|
Functional Connections Among Ponto-medullary Respiratory Neurons
APS Respiration Section
James Duffin
J. Duffin, B.G. Lindsey, H. Nimaru and J.F.R. Paton
The primary function of the central respiratory system of the medulla and
pons is to provide the automatic rhythm that drives respiratory muscles
controlling lung ventilation and upper airway patency, as well as integrate
a hierarchy of signal inputs as part of feedback control. Although much
progress has been made in investigating hypotheses about how respiratory
rhythm is generated, and several models have emerged in recent years
incorporating pacemaker hypothesis, we have reached the point where we must
still admit that network interconnections have a vital role to play. To
quote from the 2003 Annual Review of Neuroscience article by Feldman,
Mitchell and Nattie: “As yet, we do not understand the neural mechanisms
that underlie rhythm generation—they are up for grabs”. Connections among
the network of neurons involved are difficult to ascertain, but are slowly
being revealed, and the four eminent speakers of this proposed symposium
represent a cross-section of the approaches used and will both summarize
recent achievements and review past knowledge. James Duffin will act as
chairman for the symposium and also provide an introductory overview of the
interconnections among medullary respiratory neurons in decerebrate rats
in-vivo that may contribute to rhythm generation and shaping the output
to spinal and hypoglossal respiratory motoneurons. Bruce Lindsey will then
present findings from multi-site recordings in
vivo anaesthetized/decerebrate cats,
and provide direct evidence for the presence of network "modules" (multiple
correlations) in the respiratory brainstem. Hiroshi Onimaru will follow
this theme discussing findings using optical recording methods in the
in-vitro neonatal rat brainstem spinal cord preparation as well as the
presenting electrophysiological data highlighting the importance of the
opioid resistant pre-inspiratory neurons in rhythm generation. Finally
using the working heart-brainstem preparation Julian Paton will survey the
connections from somatic afferent inputs to the ponto-medullary respiratory
network. In summary, these four speakers will present an up-to-date view of
what is known about the interconnections among ponto-medullary respiratory
neurons from markedly different viewpoints provided by experiments in
several different preparations.
|
|
