Decrease in exploratory behavior in naturally occurring cholecystokinin (CCK)-A receptor gene knockout rats

Area of Science:

• Neuroscience
• Behavioral Science
• Genetics

Background:

• Cholecystokinin (CCK) is a prevalent neurotransmitter peptide in the brain.
• A specific rat strain, Otsuka Long Evans Tokushima Fatty (OLETF) rats, possesses a genetic abnormality leading to a lack of the CCK-A receptor.
• Understanding the role of CCK-A receptors in behavior is essential.

Purpose of the Study:

• To investigate potential behavioral abnormalities in OLETF rats lacking the CCK-A receptor.
• To determine if the absence of CCK-A receptor impacts exploratory behavior.
• To explore the functional significance of CCK-A receptors in the central nervous system.

Main Methods:

• Utilized open-field tests to assess behavior in OLETF rats and compare them to normal rats.
• Measured CCK release from synaptosomes.
• Quantified levels of CCK and CCK-B receptor messenger RNAs (mRNAs).

Main Results:

• OLETF rats displayed significantly reduced locomotion (hypolocomotor activity) in open-field tests.
• A decrease in the incidence of rearing behavior was observed in OLETF rats.
• CCK release, CCK mRNA, and CCK-B receptor mRNA levels were comparable between OLETF and normal rats.

Conclusions:

• The lack of CCK-A receptor in OLETF rats is associated with decreased exploratory behavior and hypolocomotion.
• The findings suggest a critical role for the CCK-A receptor in regulating motor activity and exploration.
• The absence of CCK-A receptor, not altered CCK levels or CCK-B receptor expression, appears responsible for the observed behavioral deficits.