Prevalence of vitamin A deficiency. Vitamin A deficiency (VAD) is a lack of vitamin A in humans. It is common in poorer countries but rarely seen in more developed countries. Nyctalopia (night blindness) is one of the first signs of VAD.revalence of vitamin A deficiency. Vitamin A deficiency (VAD) is a lack of vitamin A in humans. It is common in poorer countries but rarely seen in more developed countries. Nyctalopia (night blindness) is one of the first signs of VAD.
Both lithium and valproate have been reported to increase rat CSF GABA levels. Regarding valproate, animal studies reported that it enhances GABA levels, GABA synaptic release, GAD activity, neuronal GABA responsiveness, and inhibits GABA-T in several brain regions.
GABA is the major inhibitory neurotransmitter found in the CNS and, as such, is important for balancing excitatory action of other neurotransmitters. High levels of GABA may be a result of excitatory overload, or a compensatory mechanism to balance the surplus excitatory neurotransmitter activity. These high levels result in a âcalmingâ action that may contribute to sluggish energy, feelings of sedation, and foggy thinking.