| NEUROSCIENCE | PEER-REVIEW veterans with or without post-traumatic stress disorder


(PTSD), the veterans with PTSD demonstrated reduced GABAÐbenz odiazepine receptor binding, demonstrated by positron emission tomography (PET) scan. On an EEG, alpha waves are generated in a relaxed


state, while beta waves are seen in stressful situations that make mental concentration difficult. Therefore, the ratio of alpha-to-beta waves is used as an indication of relaxation and better concentration. In general, the greater the alpha-to-beta ratio, the more relaxed and alert the person is. GABA produced significant effects on both increasing alpha waves and decreasing beta waves, resulting in a highly significant increase in the alpha-to-beta wave ratio. GABA receptors are highly expressed in


the thalamus, a region of the brain involved with sleep processes. GABA- agonist drugs, such as Ambien (zolpidem) and Restoril (temazepam), are sedatives used to treat insomnia. The synthetic GABA- like drug gabapentin that increases brain GABA levels has been found to improve sleep disturbances associated with alcohol consumption. Owing to its relaxation effects, GABA may be considered as a sleep aid.


L-tryptophan/5-hydroxytryptophan L-tryptophan, a large neutral amino acid essential for human metabolism, is the metabolic precursor of serotonin (a neurotransmitter), melatonin (a neuro-hormone), and niacin (vitamin B3). It improves sleep latency. Even at low doses, it has been found to improve stage IV sleep and improve restfulness in obstructive sleep apnoea. It does not limit cognitive performance or inhibit arousal from sleep. 5-Hydroxytryptophan (5-HTP) acts primarily by increasing central nervous system (CNS) levels of serotonin. Other neurotransmitters and CNS chemicals, such as melatonin, dopamine, noradrenaline, and beta-endorphin, have also been shown to increase following oral administration of 5-HTP26–28


. The decarboxylation of 5-HTP to


serotonin is dependent on the presence of the active form of vitamin B6, pyridoxal 5Õ -phosphate (P5P), while the further conversion to melatonin requires S-adenosyl-L-methionine (SAMe). Owing to its enhancement of serotonin and then melatonin, 5-HTP benefits sleep disorders.


noradrenaline and dopamine in animals; and it appears that depletion, especially of noradrenaline, is closely related to stress-induced performance decline in animals. Administration of tyrosine, an amino acid precursor of catecholamines, alleviates depletion of brain catecholamines and stress-induced decline in performance in these animals. In humans, tyrosine supplementation appears to work in the same manner, alleviating stress-induced decline in nervous system noradrenaline, and subsequently enhancing performance under a variety of circumstances, including sleep deprivation, combat training, cold exposure, and unpleasant background noise. According to one study29


tyrosine 150 mg/


kg administration was able to offset decline in performance and vigilance for 3 hours in sleep-deprived candidates. study30


In another on cadets on a military combat


training course, the group supplied with a tyrosine-rich drink performed better in tasks involving memory and tracking versus the group receiving placebo. Tyrosine supplementation has also been shown to decrease


systolic blood pressure. In another study31


that evaluated the negative influence


of acute exposure to cold on short-term memory, it was found that tyrosine supplementation returned performance to the level found at ambient temperature. Another study demonstrated that tyrosine (100 mg/kg) supplementation improved mood and memory in individuals subjected to a 4.5-hour exposure to cold and hypoxia. Individuals taking 300 mg/kg of tyrosine better resisted stress than placebo. In a study in which subjects were given tyrosine while


In humans, sustained and continuous work


periods exceeding 12 hours, and often involving sleep


performing a number of stress-sensitive tasks, while concurrently exposed to stress-inducing 90 dB background noise, tyrosine improved performance on two cognitive tasks and transiently decreased diastolic blood pressure. Tyrosine (100 mg/kg) also enhanced measured aspects of cardiovascular and cognitive performance in subjects exposed to stress-inducing low negative-pressure sessions (-50 mm Hg) for a maximum of 30 minutes.


L-Tyrosine In humans, sustained and continuous work periods exceeding 12 hours, and often involving sleep loss and fatigue, can result in increased stress and anxiety, mood deterioration, and decreased performance. Studies suggest supplementation with tyrosine might, under circumstances characterised by psychosocial and physical stress, reduce the acute effects of stress and fatigue on task performance. Stress depletes the brain reserves of the catecholamine neurotransmitters


loss and fatigue, can result in increased stress and anxiety, mood deterioration, and decreased performance.


Neurotransmitter cofactor vitamins Thiamin (vitamin B1) Experimental and clinical results33


have shown


thiamin to be an effective nutrient in protecting the adrenal gland from functional exhaustion secondary to surgery. Intramuscular injections of thiamin in a dose of 120 mg per day, starting a few days prior to surgery and 1.5–2 hours immediately


prior to surgery, reduced the cortisol reaction, both before and at the height of the surgery. Continued administration of thiamin post-surgery prevented the usual post-surgery reduction in blood cortisol levels.


Niacinamide (vitamin B3) Fatigue is closely related to a lack of sleep and short


prime-journal.com | January/February 2013 ❚ 57


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