Nutritional Needs in Cold and High-Altitude Environments Applications for Military Personnel in Field Operations (1996) / Chapter Skim
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23 Food Components and Other Treatments That May Enhance Mental Performance at High Altitudes and in the Cold
23 Food Components and Other Treatments That May Enhance Mental Performance at High Altitudes and in the Cold
Pages 453-466
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From page 453... ...
Furthermore, when soldiers are rapidly deployed to mountainous regions, their performance of required critical duties upon arrival, including offensive or defensive operations, may be impaired. The adverse effects of cold exposure on human behavior can also be significant and can exacerbate the physical consequences of exposure to extreme cold.
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From page 454... ...
Appropriate nutritional supplements might, in theory be hood candidates for producing beneficial effects in various environments and In situations in which multistressor exposure occurs. In addition, if there are common elements in the response of the central nervous system (CNS)
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From page 455... ...
Such beneficial effects were predicted because when catecholaminergic neurons are highly active (which occurs during exposure to many acute stressors) , the amount of neurotransmitter they release increases if more tyrosine is made available (Wurtman et al., 1981)
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From page 456... ...
by sampling extracellular fluid from a small brain region to assess neurotransmitter and metabolite levels. A specially manufactured guide cannula is implanted stereotaxically onto the skull of an anesthetized animal and above a specific brain region of interest.
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From page 457... ...
It appears that by supplying additional neurotransmitter precursor to the brain by peripheral administration of tyrosine, which readily crosses the blood-brain barrier, substantial additional NE is released during exposure to acute stress. Changes in the release of particular brain neurotransmitters, while of theoretical interest, are by themselves difficult to interpret.
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From page 458... ...
The test employed, the Porsolt swim test, was previously reported to be sensitive to other catecholaminergic agonists and has been used as a screening test to help in the selection of new antidepressant drugs (Porsolt et al., 19783. The Porsolt swim test was also reported to detect the effects of various neurotransmitter precursors, including tyrosine, in relatively nonstressed animals (Gibson et al., 1982~.
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From page 459... ...
Values are expressed as mean difference scores (MDS) which equal hypothermia immobility time minus normothermia immobility time.
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From page 460... ...
These studies support the conclusion that, at least for some ofthe behavioral symptoms of hypobaric hypoxia, the cholinergic system may play a less-important role or may be more difficult to modify than the catecholaminergic system. That beneficial effects of tyrosine were detectable by very different behavioral tests, such as the MWM arid the Porsolt swim test, is encouraging with regard to the generalization of tyrosine's effects.
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From page 461... ...
The authors have also studied the effects of cold stress and restraint stress on hippocampal acetylcholine and choline levels. As shown in Figure 23-5, restraint stress causes significant reductions in acetylcholine release in the rat hippocampus.
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From page 462... ...
AUTHORS' CONCLUSIONS As noted above, exposure to different stressors, particularly those as physiologically different in their consequences as hypoxia and cold stress, may require different types of treatment. However, if there are common CNS elements to the response of organisms to stress, common treatment strategies may be useful for a wide range of dissimilar stressors.
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From page 463... ...
Galli, and A Levy 1 994 Acute cold and restraint stress alters hippocampal cholinergic neurotransmission and memory [abstract]
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From page 464... ...
Levy, and H.R. Lieberman 1993 Cold stress exposure alters hippocampal cholinergic neurotransmission.
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From page 465... ...
PERFORMANCE-ENHANCING FOOD COMPONENTS 465 Wurtman, R.J., and H.R. Lieberman 1989 Use of tyrosine and other nutrients to protect against stress and to enhance and sustain performance.
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