Project: Research project

Project Details


The proposed experiments have two goals. The first is to identify the
stimulus to the group III and IV afferents whose activation by muscular
contraction signals the central nervous system that blood supply and demand
in a working muscle are not properly matched. These afferents will be
identified by showing that they respond more to an ischemic static
contraction than to a normal contraction, even though both types of
contraction develop the same tension. Once identified, the effect on the
discharge of these afferents of arterial injections of several ischemic
metabolites, such as adenosine, lactate, phosphate and possibly ammonia
will be examined. Likewise, the effect on the discharge of these afferents
of hypoxemia, acidemia and hypercarbemia will be examined. These
experiments will be performed in unanesthetized decerebrate cats. Afferent
impulse activity arising from the triceps surae muscles will be recorded
from the dorsal roots. The second goal is to demonstrate in decorticate
unanesthetized cats that group III and IV hindlimb muscle afferents are
stimulated by a "true dynamic exercise", induced by activation of
subthalamic and mesencephalic locomotor centers. Stimulation of these
centers is known to cause a discharge pattern in alpha motoneurons that is
identical to that evoked by dynamic exercise. The effect of ischemia,
induced by occlusion of the arterial blood supply to the working muscle, on
the afferents' response to dynamic excercise will be examined. In
addition, the effect of infusing ischemic metabolites on the afferents'
discharge will be examined. In addition to showing that group III and IV
muscle afferents are stimulated by exercise, these experiments may shed new
light on the puzzling question as to the nature of the metabolic stimulus
causing these afferents to signal the central nervous system that blood
supply and demand in a contracting muscle are mismatched.
Effective start/end date1/1/901/1/90


  • National Heart, Lung, and Blood Institute

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