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Psychopharmacology

, Volume 148, Issue 2, pp 124–131 | Cite as

The role of genetic and early environmental factors in determining apomorphine susceptibility

  • Bart A. Ellenbroek
  • Frans Sluyter
  • Alexander R. Cools
Original Investigation

Abstract 

Rationale: There is ample evidence that rats show large individual differences in their response to dopaminergic drugs, such as apomorphine. Objective: The aim of the present study was to investigate the role of genetic and (early) environmental factors in determining the adult susceptibility to apomorphine. Four experiments were performed: In experiment 1, the original selective breeding of rats for apomorphine susceptibility (leading to APO-SUS and APO-UNSUS rats) was extended and replicated in an independent group of Wistar rats. In experiment 2, APO-SUS males were cross-bred with APO-UNSUS females and vice versa. In experiment 3 APO-SUS litters were cross-fostered to APO-UNSUS mothers or infostered to unknown APO-SUS mothers and vice versa. In experiment 4 APO-SUS and APO-UNSUS rats were maternally deprived on postnatal day 9, for a single 24-h period. Methods: Adult rats were subcutaneously injected with 1.5 mg/kg apomorphine and their gnawing response was automatically recorded in a gnawing box for 45 min. Results: In experiment 1, the original breeding was extended up to generation 24, leading to a strong and consistent difference in gnawing scores. The replication experiment also succeeded in differentiating APO-SUS and APO-UNSUS. The cross breeding experiments showed that the APO-SUS/UNSUS offspring showed gnawing scores in between the original selection lines. Cross-fostering APO-SUS with APO-UNSUS significantly reduced the gnawing response in the offspring, whereas it did not affect the gnawing score in the APO-UNSUS animals. Maternal deprivation had the opposite effect: increase in gnawing response in APO-UNSUS, with no effect in APO-SUS. Conclusion: The results show a clear-cut contribution of both genetic and early environmental factors to the susceptibility of apomorphine.

Key words Apormorphine Genetic factor Environmental factor Susceptibility 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Bart A. Ellenbroek
    • 1
  • Frans Sluyter
    • 1
  • Alexander R. Cools
    • 1
  1. 1.Department of Psychoneuropharmacology, University of Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands e-mail: A.Ellenbroek@pnf.kun.nl, Fax: +31-24-3540044NL

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