DHA in Mechanisms of Sympathetic System/Parasympathetic System (SS/PSS) Homeostasis in Development

Recently, in an article by Pivik et al.,it was postulated that early infant diet supplemented with the omega 3 fatty acid DHA effects on resting cardiovascular activity and behavioral development during the first half-year of life(9). On this occasion it may be useful to comment on the possible mechanisms of this deactivation of parasympathetic system in response to decreased DHA in diet as observed as decreased heart rate, to better explain the underlying causes of this empirical observation. Docosahexaenoic acid (DHA), being an omega-3 fatty acid or in other words a long chain polyunsaturated fatty acid is one of the major components of the cerebral cortex and visual system, where they play a critical role in neural development. It is most concentrated in structures local to the brain stem and diencephalon, particularly the basal ganglia, limbic regions, thalamus and midbrain, and comparatively lower in white matter. Dietary supplementation increases DHA in all these structures except the cerebral cortex and cerebellum(7). Although cognitive performance in humans and experimental animals can be improved by administering the DHA, the neurochemical mechanisms underlying this effect remain uncertain. In general, nutrients or drugs that modify brain function or behavior do so by affecting synaptic transmission, usually by changing the quantities of particular neurotransmitters present within synaptic clefts or by acting directly on neurotransmitter receptors or signal-transduction molecules. It has been found that DHA also affects synaptic transmission in mammalian brain: Brain cells of gerbils or rats receiving this fatty acid manifest increased levels of phosphatides and of specific pre- or post-synaptic proteins. They also exhibit increased numbers of dendritic spines on postsynaptic neurons(8). Omega-3 fatty acids play crucial roles in the development and function of the central nervous system. These components, which must be obtained from dietary sources, have been implicated in a variety of neurodevelopmental and psychiatric disorders. The factors that regulate adult neurogenesis are highly conserved among species, In animals where cells in S-phase of the cell cycle are detected, a quantitative analysis of the resulting BrdU-labeled cells in the projection neuron cluster in the brain shows that short-term augmentation of dietary omega-3 relative to omega-6 fatty acids results in significant increases in the numbers of S-phase cells, and that the circadian pattern of neurogenesis is also altered. It is proposed that the ratio of omega-3:omega-6 fatty