Effect of skeletal muscle fiber type on the pressor response evoked
by static contraction in the rabbit.
Wilson, L. Britt, Christopher K. Dyke, Dorabeth Parsons, P. Tim Wall,
James A. Pawelczyk, R. Sanders Williams, and Jere H. Mitchell.
Moss Heart Center and Departments of Physiology and Internal
Medicine, U.T. Southwestern Medical Center, 5323 Harry Hines Blvd.,
Dallas, Texas 75235-9034
APStracts 2:0327A, 1995.
The purpose of this study was to determine if the reflex hemodynamic
responses to static contraction of predominately glycolytic muscle
are greater than the changes elicited by primarily oxidative muscle.
Low-frequency electrical stimulation (continuous 21 days) of the
tibial nerve of one hindlimb of adult rabbits converted the metabolic
characteristics of the predominately glycolytic gastrocnemius to a
muscle that was primarily oxidative. After 21 days of stimulation,
the rabbits were decerebrated and static contraction of the
glycolytic muscle (unstimulated gastrocnemius) initially decreased
heart rate (HR) -16+/-3 beats/min and mean arterial pressure (MAP)
-17+/-3 mmHg. Thereafter, MAP increased 13+/-3 mmHg above baseline.
Static contraction of the oxidative muscle (stimulated gastrocnemius)
produced similar decreases in HR and MAP (-12+/-4 beats/min and
-12+/-3 mmHg). However, the subsequent increase in MAP (8+/-3 mmHg;
above baseline) was less than that evoked by contraction of the
glycolytic muscle. The responses evoked by stretch of each muscle and
high intensity electrical stimulation were the same, indicating the
afferents from the muscle were not destroyed by the chronic
stimulation technique. These results support the hypothesis that
metabolic by-products play an important role in the pressor response
to static contraction of skeletal muscle. In addition, these data
confirm that contraction of predominately oxidative muscle can evoke
a reflex pressor response, albeit smaller than the change elicited
from primarily glycolytic muscle.
Received 14 March 1995; accepted in final form 8 July 1995.
APS Manuscript Number A281-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.