1. Brazilian Journal of Medical and Biological Research
Joey Miller
Effects of Caffeine on Learning and Memory in Rats Tested in the Morris Water Maze
Angelucci, M.E.M.; Cesário, C.; Hiroi, R.H.; Rosalen, P.L.; Da Cunha, C.
Brazilian Journal of Medical and Biological Research
Vol. 35 (10), October 2002, pp

2. Hypothesis
Caffeine will have an improving effect on memory functions.

3. Structure Subjects 13 Groups of 12 Adult Male Wistar Rats (240-300 g)
Tools
Morris Water Maze (Spatial Version)
Training and Test Sessions
Training Sessions – 6 Trials
Test Sessions– 3 Trials (48 Hours after Training Session.)

4. Independent Variables
Administration Time
3 Levels:
Pre-Training, Post-Training, Pre-Test
Amount of Caffeine
(0-30 mg/kg, ip, in .1 ml/100 g Body Weight)
Pre-Training – Saline, 3, 10, 30 mg/kg
Post-Training – Saline, .3, 3, 10, 30 mg/kg
Pre-Test – Saline, 3, 10, 30 mg/kg

5. Dependent Variables Memory and Learning
Test and Training scores on tests of:
Distance Traveled (cm)
Escape Latency (seconds)

6. Theoretical Constructs
Learning
Memory Acquisition
Memory
Retention and Retrieval

7. Operational Definition
Learning
Training Portion
Measurements of Distance traveled and Escape Latency during Training.
Memory
Test Portion
Measurements of Distance traveled and Escape Latency during Testing.

8. Statistical Analysis ANOVA Two-way
Training and Test Data analyzed separately
Number of Trials as repeated measure
Differences between groups were evaluated by the post hoc Duncan test.

9. Results
Caffeine improved memory retention but not memory acquisition (learning).
Post-Training Administration
Improved memory retention at doses of mg/kg, but not at doses of 30 mg/kg
Pre-Test Administration
Small increase in memory retrieval
Pre-Training Administration
Did not alter performance in Training or Test sessions

10. Results Pre-Training Administration
Treatment did not affect training for treatment and interaction treatment vs. repeated measure (P≥0.2), or test scores (P≥0.2).
Post-Training Administration
During Training no difference among groups for latency (p≥0.2) and Traveled Distance (p=.10).
Repeated Measure: latency and traveled distance, p≤0.001
Treatment: latency, p≤0.05; traveled distance, p=.18
Interaction Treatment vs. Repeated Measure: latency, p≤0.01; traveled distance, p≤0.05
Test Sessions showed that mg/kg of caffeine improved retention (P≤0.05 Post Hoc Duncan Test). While the dose of 30 mg/kg had no effect (p=.14 Post Hoc Duncan Test).

11. Results Pre-Test Administration
Groups did not differ in training sessions for latency, and it had no effect on retention.
The shape of the retention (test) curve implied the low doses of caffeine tend to improve memory retrieval (interaction treatment vs. repeated measure, traveled distance: p≤0.05, latency: p≥0.2)

12. Conclusion
Effect of caffeine was more evident when administered after training. This suggests an effect on memory consolidation.
Ineffective when administered before training. Suggesting that it does not affect working memory and memory acquisition.
The effect of Pre-Testing administration suggest improvement in memory retrieval (for spatial memory tasks).

13. Conclusion
The improving effect of caffeine in smaller doses, and impairment or no effect at higher doses, suggest an effect on more than one type of receptor.
Effects of caffeine are better explained as antagonists of the Adenosine A2 receptors

14. Discussion Well conducted study
Good attempts at controlling confounding variables
Applicable to human species?
It was noted that rats have similar hippocampal memory systems
Would the results for female rats have been the same?
How would subjects under different natural conditions respond?
How would prior caffeine use effect these results?