AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 4 578-R586, Copyright © 1984 by American Physiological Society
Genetic and environmental influences on developing autonomic control of heart rate
D. C. Tucker, R. K. Bhatnagar and A. K. Johnson
Individual differences in cardiovascular regulation result from a dynamic
interaction between genetically programmed developmental processes and
extrinsic (environmental) conditions. The alterations in autonomic
functioning previously identified among pups of the spontaneously
hypertensive rat (SHR) strain suggest a genetic influence on autonomic
development. In the present studies, an early stimulation procedure
previously shown to reduce the behavioral and endocrine responsiveness of
rodents in adulthood was demonstrated to alter both neural control of heart
rate and regional brain catecholamine levels during the preweaning period.
Pups from litters of SHR and Wistar-Kyoto (WKY) rats were handled daily
during the first postnatal week. Selective pharmacological blockade with
atenolol and atropine methylnitrate was used to identify autonomic controls
of heart rate at 16 and 28 days of age. Combined blockade was used to
estimate intrinsic heart rate. In both SHR and WKY, early handling was
associated with elevated basal heart rate, elevated intrinsic heart rate,
and decreased sympathetic tone. Parasympathetic influence on heart rate was
elevated by early handling in WKY and decreased by handling in SHR. In
addition, an increase in dorsal cortical norepinephrine concentration was
produced by early handling in both strains. These data suggest that early
environmental conditions can interact with the genetic predisposition for
elevated blood pressure and may play a potentially important role in
organizing the neural controls of cardiovascular regulation.
