, Volume 168, Issue 4, pp 417–425 | Cite as

Targeted mutation of CCK2 receptor gene modifies the behavioural effects of diazepam in female mice

  • Sirli Raud
  • Kertu Rünkorg
  • Alar Veraksitš
  • Ain Reimets
  • Aleksei Nelovkov
  • Urho Abramov
  • Toshimitsu Matsui
  • Michel Bourin
  • Vallo Volke
  • Sulev KõksEmail author
  • Eero Vasar
Original Investigation



Evidence suggests that GABA and CCK have opposite roles in the regulation of anxiety.


The aim of the present work was to study diazepam-induced anxiolytic-like action and impairment of motor co-ordination, and the parameters of benzodiazepine receptors in mice lacking CCK2 receptors.


The action of diazepam (0.5–3 mg/kg IP) was studied in the elevated plus-maze model of anxiety and rotarod test using mice lacking CCK2 receptors. The parameters of benzodiazepine receptors were analysed using [3H]-flunitrazepam binding.


In the plus-maze test, the exploratory activity of the homozygous (−/−) mice was significantly higher compared to their wild-type (+/+) littermates. However, the wild-type (+/+) mice displayed higher sensitivity to the anxiolytic-like action of diazepam. Even the lowest dose of diazepam (0.5 mg/kg) induced a significant increase of open arm entries in the wild-type (+/+) mice. A similar effect in the homozygous (−/−) mice was established after the administration of diazepam 1 mg/kg. The highest dose of diazepam (3 mg/kg) caused a prominent anxiolytic-like effect in the wild-type (+/+) mice, whereas in the homozygous (−/−) animals suppression of locomotor activity was evident. The performance of the homozygous (−/−) mice in the rotarod test did not differ from that of the wild-type (+/+) littermates. However, a difference between the wild-type (+/+) and homozygous (−/−) animals became evident after treatment with diazepam. Diazepam (0.5 and 3 mg/kg) induced significantly stronger impairment of motor co-ordination in the homozygous (−/−) mice compared to their wild-type (+/+) littermates. The density of benzodiazepine binding sites was increased in the cerebellum, but not in the cerebral cortex and hippocampus, of the homozygous (−/−) mice.


Female mice lacking CCK2 receptors are less anxious than their wild-type (+/+) littermates. The reduced anxiety in homozygous (−/−) mice probably explains why the administration of a higher dose of diazepam is necessary to induce an anxiolytic-like action in these animals. The highest dose of diazepam (3 mg/kg) induced significantly stronger suppression of locomotor activity and impairment of motor co-ordination in the homozygous (−/−) mice compared to the wild-type (+/+) littermates. The increase in the action of diazepam is probably related to the elevated density of benzodiazepine receptors in the cerebellum of homozygous (−/−) mice. The present study seems to be in favour of increased tone of the GABAergic system in mice without CCK2 receptors.


Targeted mutagenesis Wild-type Heterozygous Homozygous Benzodiazepine receptors GABA Diazepam Cholecystokinin Cholecystokinin2 receptors Rotarod test Motor co-ordination Elevated plus-maze Exploratory behaviour Anxiety 



This study was supported by the James S. McDonnell Foundation (USA) and by grant no. 3922 of the Estonian Science Foundation.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Sirli Raud
    • 1
  • Kertu Rünkorg
    • 1
  • Alar Veraksitš
    • 1
  • Ain Reimets
    • 1
  • Aleksei Nelovkov
    • 1
  • Urho Abramov
    • 1
  • Toshimitsu Matsui
    • 2
  • Michel Bourin
    • 3
  • Vallo Volke
    • 1
  • Sulev Kõks
    • 1
    Email author
  • Eero Vasar
    • 1
  1. 1.Department of Physiology, BiomedicumUniversity of TartuTartuEstonia
  2. 2.Division of Hematology/Oncology, Department of MedicineKobe University School of MedicineKobeJapan
  3. 3.Department of PharmacologyUniversity of NantesNantes CedexFrance

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