Psychosomatic Medicine 33:445-457 (1971)
© 1971 American Psychosomatic Society

Individual Differences in Autonomic Responsivity in the Adult Rat

Neonatal Influences

¹ Department of Psychology, University College, Cardiff, Wales; and The Rockefeller University New York, NY.

David A. Blizard, PhD, The Rockefeller University, East 66 St and York Ave, New York, NY 10021.

Compared with undisturbed controls, rats handled on Days 1-7 of life exhibited diminished cardiac response to handling and to novel stimulation at 100 days of age. Previous handling had a greater effect in females. Defecation scores were significantly reduced by prior handling, although correlation between measures of heart rate and defecation frequency was not significant. Between the groups, behavioral measures did not appear to be responsible for differences in heart rate. In adulthood, females had higher heart rates after handling than did males; these differences reflected differences in reactivity, as there were no differences in heart rate between sexes after they had adapted to the test situation. Heart rate correlated negatively with body weight across both sexes. Within-sex correlations of heart rate and body weight were also negative but generally not significant. If confirmed, the data indicate an effect of experimental factors on heartrate reactivity which may have important clinical implications.

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