, Volume 190, Issue 4, pp 555–568 | Cite as

Evaluation of reward processes in an animal model of depression

  • David A. Slattery
  • Athina Markou
  • John F. Cryan
Original Investigation



Anhedonia is a core symptom of major depression. Deficits in reward function, which underlie anhedonia, can be readily assessed in animals. Therefore, anhedonia may serve as an endophenotype for understanding the neural circuitry and molecular pathways underlying depression.


Surprisingly, there is scant knowledge regarding alterations in brain reward function after olfactory bulbectomy (OB), an animal model which results in a behavioural syndrome responsive to chronic antidepressant treatment. Therefore, the present studies aimed to assess reward function after bulbectomy.

Materials and methods

The present study utilized sucrose preference, cocaine-induced hyperlocomotion and intra-cranial self-stimulation (ICSS) responding to examine reward processes in the OB model.


Bulbectomized animals showed a marked preference (>90%) for 0.8% sucrose solution compared with water; similar to the preference exhibited by sham controls. Importantly, there were pronounced deficits in brain reward function, as assessed using ICSS, which lasted 8 days before returning to baseline levels. Furthermore, bulbectomized animals were hyper-responsive to the locomotor stimulating properties of an acute and a repeated cocaine regimen. However, no difference in ICSS facilitation was observed in response to an acute cocaine injection.


Taken together, these results suggest that bulbectomized rats display alterations in brain reward function, but these changes are not long-lasting and thus, not amenable to investigating the effects of pharmacological interventions. However, given that OB animals are hypersensitive to drugs of abuse, bulbectomy may be an appropriate inducing factor for the development of animal models of co-morbid depression and drug dependence.


Animal model Reward Depression Antidepressant 



The authors would like to thank Dr Cedric Mombereau, Hugo Buerki and Stefan Imobersteg for their technical assistance and Mr. Mike Arends for editorial assistance. This work was supported by National Institutes of Mental Health/National Institute on Drug Abuse Grant U01 MH69062.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • David A. Slattery
    • 1
    • 4
  • Athina Markou
    • 2
  • John F. Cryan
    • 1
    • 3
  1. 1.Neuroscience ResearchNovartis Institutes for BioMedical Research, Novartis Pharma AGBaselSwitzerland
  2. 2.Department of Psychiatry, School of MedicineUniversity of California, San DiegoLa JollaUSA
  3. 3.Department of Pharmacology and Therapeutics, School of PharmacyUniversity College CorkCorkIreland
  4. 4.Institute of ZoologyUniversity of RegensburgRegensburgGermany

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