Irt>t schedule controlled behavior in 'learned-helpless' rats: effects from a cannabinoid agonist.
C B Willmore, G D Kohler, Alexandros Makriyannis
Neuropharmacology July 2006 DOI: 10.1016/j.neuropharm.2006.03.006 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Controlled animal experiment (comparison of bred cLH and Sprague-Dawley rats) Peer reviewed |
|---|---|
| Sample size | 14 |
| Population | Congenital learned helplessness (cLH) rats (n=9) and normally bred Sprague-Dawley rats (n=5) |
| Interventions | AM 411 AM 251 diluent (vehicle) |
| Dose | moderate and high doses (exact values not stated) |
| Measures | irt>12s schedule histograms (interresponse time frequency distributions), operant schedule compliance, motor responsiveness |
| Key findings | AM 411, a CB1 receptor selective agonist, increased operant schedule compliance and normalized interresponse-time distributions in cLH rats, an effect blocked by prior injection of the CB1 antagonist AM 251. The authors report that AM 411 increased timing acuity in rats prone to behavioral despair but had opposite timing effects in normally bred Sprague-Dawley rats. |
Abstract
Human depression is partly a congenital disorder. Aspects of the behavior accompanying depression can be magnified by genetic manipulation of bred animal species. Learned Helplessness (LH) is a trait-mark behavior that successfully breeds in rodents. Here, 'congenital' LH (cLH) rats were trained to recognize and respond to 12s long interval cues (irt>12s schedule). Rats compliant to an irt>t schedule will space responses evenly and respond rhythmically. Irt>t schedule derived data are plotted in histograms showing irt (interresponse time) frequencies. A pause response peak emerges, for outbred rats, at irt values approximating the minimum interval for reinforcement. cLH rats [n=9] complied poorly to schedule contingencies when diluent (vehicle) was injected before testing. Moderate and high dose injections of a CB 1 receptor selective agonist drug (AM 411), however, increased operant schedule compliance and normalized the cLH rats' irt>t histogram distributions. Performance indicators for cLH rats are presented alongside coordinate measures from a comparison group [n=5] of normally bred Sprague-Dawley (SD) rats. In both cLH and SD rats, treatment session histograms revealed shifts of the pause response peak not accompanied by a change in motor responsiveness. The irt>12s histogram shifts were absent when AM 411 dosages were arranged to follow pre-medication injections of a CB 1 receptor selective antagonist drug (AM 251). In short, AM 411 increased timing acuity in rats prone to behavioral despair but had opposite timing effects in normally bred SD rats.