Related Experiment Video
Updated: Aug 8, 2026
07:51
Administration of Δ9-Tetrahydrocannabinol (THC) in Adolescent and Adult Mice
Published on: August 1, 2025
Irt>t schedule controlled behavior in 'learned-helpless' rats: effects from a cannabinoid agonist
C B Willmore1, G D Kohler, A Makriyannis
1University of Maryland, School of Pharmacy, Department of Pharmaceutical Sciences, Baltimore, MD 21201, USA. cwillmor@rx.umaryland.edu
Neuropharmacology
|June 7, 2006
Summary
Congenital learned helplessness (cLH) in rats impairs operant schedule compliance. A CB1 receptor agonist (AM 411) improved timing and normalized behavior in cLH rats, suggesting a therapeutic target for behavioral despair.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Genetics
Background:
- Human depression has congenital components, with learned helplessness (LH) being a heritable behavior in rodents.
- Congenital LH (cLH) rats exhibit poor performance in operant conditioning tasks.
Purpose of the Study:
- To investigate the effects of a CB1 receptor agonist (AM 411) on operant schedule compliance in cLH rats.
- To explore the potential of CB1 receptor modulation for treating behavioral despair.
Main Methods:
- cLH rats were trained on an interval > 12s (irt>12s) schedule, measuring interresponse time (irt) frequencies via histograms.
- Rats received injections of vehicle, CB1 agonist (AM 411), or CB1 antagonist (AM 251) prior to testing.
- Performance was compared to normally bred Sprague-Dawley (SD) rats.
Main Results:
- cLH rats showed poor schedule compliance with vehicle injection.
- AM 411 treatment normalized irt histogram distributions and improved schedule compliance in cLH rats.
- AM 411 shifted the pause response peak in both cLH and SD rats, but this effect was blocked by AM 251.
Conclusions:
- CB1 receptor agonism enhances timing acuity in rats with congenital learned helplessness.
- AM 411 demonstrates potential for improving behavioral despair-related deficits.
- Timing effects of AM 411 differ between cLH and normal rats, indicating complex CB1 receptor involvement.
