Cocaine self-administration improves performance in a highly demanding water maze task
Psychopharmacology, 2007•Springer
Rationale Long-term potentiation (LTP) is considered to be a cellular substrate of learning
and memory. Indeed, the involvement of LTP-like mechanisms in spatial learning has
consistently been demonstrated in the Morris water maze test. We have previously shown
that hippocampal LTP in Lewis rats was modulated by cocaine self-administration, although
the performance of cocaine-self-administered rats in the Morris water maze was not altered.
Objective Given that the ease of the task previously used could have masked any possible …
and memory. Indeed, the involvement of LTP-like mechanisms in spatial learning has
consistently been demonstrated in the Morris water maze test. We have previously shown
that hippocampal LTP in Lewis rats was modulated by cocaine self-administration, although
the performance of cocaine-self-administered rats in the Morris water maze was not altered.
Objective Given that the ease of the task previously used could have masked any possible …
Rationale
Long-term potentiation (LTP) is considered to be a cellular substrate of learning and memory. Indeed, the involvement of LTP-like mechanisms in spatial learning has consistently been demonstrated in the Morris water maze test. We have previously shown that hippocampal LTP in Lewis rats was modulated by cocaine self-administration, although the performance of cocaine-self-administered rats in the Morris water maze was not altered.
Objective
Given that the ease of the task previously used could have masked any possible effects of the cocaine-induced LTP enhancement on spatial learning, a new and more difficult water maze task was devised to address this issue.
Materials and methods
Animals self-administered cocaine (1 mg/kg) or saline under a fixed ratio 1 schedule of reinforcement for 22 days. Spatial learning was assessed in a difficult water maze task (four sessions, two trials per session with a 90-min intertrial interval), and spatial memory was also evaluated 48 h after training (a 90-s test). Additionally, reversal learning and perseverance were also studied.
Results
There was a reduced latency in finding the hidden platform during training, as well as improved memory of the platform location in cocaine-self-administered rats with respect to animals that self-administered saline. No differences were observed in reversal learning or perseverance between groups.
Conclusions
Our data suggest that cocaine self-administration facilitates learning and memory in the water maze test only when animals are submitted to highly demanding tasks, involving working memory or consolidation-like processes during the intertrial interval.
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