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Age-dependent correlation of motor performance with neurotransmitter synthetic enzyme activities in mice
Abstract:
The performance of male C57BL/6J mice (Mus musculus) was assessed in a battery of tests designed to detect age-related losses in motor abilities and also to examine individual differences within age groups. Studied were 4-, 18-, and 24-month-old mice. Within 5 days following the completion of the behavioral battery, the mice were killed, and brain tissue was taken for determinations of choline acetyltransferase (EC 2.3.1.6), L-glutamic acid decarboxylase (EC 4.1.1.15) and tyrosine hydroxylase (EC 1.14.16.2) activities in the frontoparietal + temporal + occipital cortex, hippocampus, striatum, and cerebellum. Two composite test scores were derived for each animal. The first composite score comprised measurements of locomotor activity, and the second reflected strength and coordination abilities. Test scores included in each composite correlated highly with that composite score, but not with the other composite. This observation suggests that there is a high degree of internal consistency for the composite scores and that the composite scores represent independent behavioral factors. Significant correlations between the composite scores and regional enzyme activities were detected; these correlations varied with age. In most cases, the sign (+, -) of the correlation was reversed at 24 months as compared with 4 months of age. These results suggest that the relations between performance and enzyme activities vary with age, and may reflect altered neurotransmitter function during senescence. This work serves as an example of how direct correlational analyses may help to elucidate behavioral-neurochemical interactions in aging.
Insights
Aging mice show altered brain enzyme activity linked to motor function decline. Enzyme-behavior correlations change with age, suggesting shifts in neurotransmitter function during senescence.
Area of Science:
- Neuroscience
- Gerontology
- Behavioral Biology
Background:
- Age-related motor deficits are common in mammals.
- Understanding the neurochemical underpinnings of these changes is crucial for interventions.
Purpose of the Study:
- To investigate the relationship between age-related motor performance and specific brain enzyme activities in male C57BL/6J mice.
- To examine how these relationships change across different ages (4, 18, and 24 months).
Main Methods:
- Mice of three age groups underwent a battery of behavioral tests assessing locomotor activity, strength, and coordination.
- Post-mortem brain tissue was analyzed for choline acetyltransferase, L-glutamic acid decarboxylase, and tyrosine hydroxylase activities in specific regions.
- Correlational analyses were performed between composite behavioral scores and regional enzyme activities.
Main Results:
- Two independent composite behavioral scores (locomotor activity and strength/coordination) were derived.
- Significant correlations were found between behavioral scores and enzyme activities, varying with age.
- The direction of correlations often reversed between young (4 months) and old (24 months) mice.
Conclusions:
- Behavioral performance and brain enzyme activities are linked, with this relationship changing significantly with age.
- These age-dependent correlations suggest altered neurotransmitter system function during aging.
- Direct correlational analyses are valuable for understanding behavioral-neurochemical interactions in aging.