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Long-Term Effects of Early Social Isolation in Macaca mulatta: Changes in Dopamine Receptor Function Following Apomorphine Challenge
  • Mark H. Lewis, University of North Carolina
  • John P. Gluck, University of New Mexico
  • Tom L. Beauchamp, University of New Mexico
  • Michael F. Keresztury, University of North Carolina
  • Richard B. Mailman, University of North Carolina
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The hypothesis that early social isolation results in long-term alterations in dopamine receptor sensitivity was tested using older adult rhesus monkeys. Isolated and control monkeys were challenged with apomorphine (0.1 and 0.3 mg/kg), and the drug effects on spontaneous blink rate, stereotyped behavior, and self-injurious behavior were quantified using observational measures. Monoamine metabolites were quantified from cisternal CSF by HPLC-EC, prior to pharmacological challenge. Isolated and control monkeys did not differ in CSF concentrations of HVA, 5-HIAA, or MHPG. At the higher dose, apomorphine significantly increased the rate of blinking, the occurrence of whole-body stereotypies, and the intensity of stereotyped behavior (as measured by observer ratings) in isolated monkeys. The frequency of occurrence of self-injurious behavior was too low to allow for meaningful comparisons. These significant differences in response to apomorphine challenge support the hypothesis that long-term or permanent alterations in dopamine receptor sensitivity, as assessed by drug challenge, are a consequence of early social deprivation.


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Citation Information
Lewis, M. H., Gluck, J. P., Beauchamp, A. J., Keresztury, M. F., & Mailman, R. B. (1990). Long-term effects of early social isolation in Macaca mulatta: changes in dopamine receptor function following apomorphine challenge. Brain Research, 513(1), 67-73.