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Undernutrition of weanling and adult rats: effects on operant responding
Insights
Undernutrition in rats, even after brain growth, alters behavior, increasing responsiveness to food rewards. This suggests developmental stage may not solely determine long-term behavioral changes from nutritional deficits.
Area of Science:
- Neuroscience
- Behavioral Science
- Nutritional Science
Background:
- Brain development in rats is highly sensitive to undernutrition during the suckling period.
- Undernutrition during early life is presumed to cause lasting behavioral changes due to impaired brain growth.
Purpose of the Study:
- To investigate if undernutrition at later life stages, with minimal impact on brain growth, also induces lasting behavioral alterations.
- To challenge the assumption that behavioral changes from undernutrition are solely linked to brain growth deficits.
Main Methods:
- Rats were subjected to undernutrition after weaning (25-67 days) or in adulthood (80-134 days).
- Behavioral testing occurred 3-4 months post-undernutrition using variable interval and variable ratio schedules with food reinforcement.
Main Results:
- Rats undernourished post-weaning or in adulthood exhibited higher response rates on reinforcement schedules compared to controls.
- Behavioral patterns in later-stage undernourished rats mirrored those of suckling-period undernourished rats.
Conclusions:
- Undernutrition at various life stages, not just during critical brain growth periods, can lead to enduring behavioral changes.
- These changes may involve increased responsiveness to food rewards following deprivation, potentially mediated by a cognitive mechanism.
Abstract:
In the rat, brain growth is most vulnerable to undernutrition during the suckling period. Undernutrition at that stage also produces lasting effects on behaviour and it is often assumed that these are due to disturbances of brain growth. The proposal that this may not necessarily be so was explored by testing the behaviour of rats which had been undernourished at later stages of life and which, therefore, would be expected to show little or no deficit in brain growth. Rats were undernourished either immediately after weaning (25-67 days) or in adulthood (80-134 days) and were tested 3-4 months later on variable interval and variable ratio schedules of reinforcement with food as the reward. Their behaviour on these schedules was similar to that of rats undernourished during the suckling period: both groups responded or tended to respond at a higher rate than controls. Hence, it is possible that undernutrition at any stage in life may make animals more responsive to food when deprived subsequently. A cognitive mechanism for this change in behaviour is suggested.