Responses of SHR to combinations of chemical sympathectomy, adrenal demedullation, and training
C. M. Tipton, M. S. Sturek, R. A. Oppliger, R. D. Matthes, J. M. Overton and J. G. Edwards
The single and combined influences of exercise training, chemical
sympathectomy (SYMX), and surgical adrenal demedullation (D) were examined
in four separate spontaneously hypertensive rat (SHR) groups. SYMX was
accomplished by subcutaneous injections of antinerve growth factor (ANGF)
over a 5-day period after birth followed by 20 separate injections of
guanethidine sulfate during a 27-day period. Measurements of urine, plasma,
or tissue levels of catecholamines indicated that these experimental
procedures were effective. The animals were exercise trained (T) for 10 wk
or longer at 40-60% of their VO2max capacity, and all T groups exhibited
longer run times or higher muscle cytochrome oxidase activity; however,
only the SHR + T subgroup had a significantly higher VO2max value than its
control (NT). Training lowered resting systolic blood pressure (SBP) in the
SHR subgroup but normalization of SBP occurred only with SYMX.
Interestingly, only the SYMX + T subgroup with intact adrenal glands also
had lower SBP values than the NT. The SHR + T and SYMX + T subgroups but
not the SYMX + D + T had less cardiac acceleration after ip injections of
atropine than their controls. Heavier heart weights were observed only in
the SHR + T subgroup; SYMX was associated with lighter heart weights
regardless of whether the rats had been T or D. These collective findings
demonstrated again the importance of the sympathetic nervous system to an
exercise response, suggesting that an intact adrenal medulla was essential
for SHR groups to achieve many of the adaptations associated with training.
Am J Physiol Heart Circ Physiol 247: H109-H118, 1984;
0363-6135/84 $5.00
