jimmylegs wrote:
reminds me of what my neuro said about elevated uric acid, anon. i didn't get it at the time but it does make sense now (as one of many consequences of poor nutrient status, zinc in particular).
this was interesting:
Enhancement of social isolation-induced aggressive behavior of young mice by zinc deficiency. (2008)
http://www.ncbi.nlm.nih.gov/pubmed/18374363Abstract
Neuropsychological behavior via activation of the hypothalamic-pituitary-adrenal (HPA) axis was analyzed using young mice fed a zinc-deficient diet for 2 weeks. Serum corticosterone concentration was significantly increased after 2-week zinc deprivation, whereas zinc concentration in the brain was not decreased. In the resident-intruder test, the rate of mice that exhibited aggressive behavior to the total mice was significantly higher in isolated zinc-deficient mice than in isolated control mice. The duration of aggressive behavior was more in isolated zinc-deficient mice. These results indicate that aggressive behavior of young mice elicited by social isolation is enhanced by zinc deficiency. On the other hand, social isolation-induced aggressive behavior was enhanced in isolated pair-fed mice with food restriction that can activate the HPA axis. Serum corticosterone concentration was also significantly higher in isolated zinc-deficient mice. To see the effect of the increased serum corticosterone on behavioral abnormality, neurotransmitter concentrations in brain tissue were checked. The concentrations of glutamate and GABA in brain tissue were significantly higher in both grouped and isolated zinc-deficient mice. Furthermore, the concentration of extracellular glutamate in the amygdala before the resident-intruder test was significantly higher in isolated zinc-deficient (aggressive) mice and the higher concentration was maintained during the test. The changes in neurotransmitter homeostasis, probably via the increase in serum corticosterone, seem to be linked to aggressive behavior elicited by social isolation in zinc deficiency
Jimmylegs,
I am cracking up because no matter how many times I read that study, I can't figure out the point you are trying to make. Duurrr. I dug up these studies linking zinc to hippocampus/hpa-axis though. I don't know what to think about zinc supplementation now...
http://onlinelibrary.wiley.com/doi/10.1 ... 587.x/fullQuote:
Zinc is concentrated in certain CNS excitatory tracts, especially in hippocampal mossy fibres where it has been suggested to modulate synaptic transmission and plasticity. Using rat mossy fibre synaptosomes depolarized by 4-aminopyridine, we show here that low zinc concentrations restore the membrane potential and reduce glutamate release. Both effects arose from activation of ATP-sensitive potassium channels (KATP), since they were mimicked by the KATP opener diazoxide and antagonized by the KATP blocker tolbutamide. Using recombinant channels expressed in COS-7 cells, we confirmed that micromolar zinc did activate KATP of the type found in hippocampus. We tested the hypothesis that this action of zinc could be beneficial during an ischaemic challenge by using organotypic hippocampal slice cultures. When zinc was applied at micromolar concentrations during a brief anoxic-hypoglycaemic episode, it significantly attenuated the ensuing neuronal death, whereas chelation of endogenous zinc markedly aggravated cell damage. Protective effect of zinc was mediated through KATP, as was shown by using the opener diazoxide and the blocker tolbutamide. Thus, by activating pre-synaptic KATP channels, zinc protects neurones from hyper-excitation, excessive transmitter release and exitotoxicity, and may thus act as an endogenous neuroprotector in conditions such as epilepsy or stroke.
This one seems to conflict with your mouse-agression study. I don't get it.
http://onlinelibrary.wiley.com/doi/10.1 ... ated=falseQuote:
Abstract
Approximately 10% of total zinc in the brain exists in synaptic vesicles of glutamatergic neurons; however, the function of vesicular zinc is poorly understood. The presynaptic action of zinc against excitatory and inhibitory neurotransmission was studied in rat hippocampus using in vivo microdialysis. When the hippocampal CA3 region was perfused with 10–300 μM ZnCl2, the level of glutamate in the perfusate was decreased, whereas the level of γ-aminobutyric acid (GABA) was increased. Chelation of endogenous zinc with CaEDTA increased the glutamate level in the perfusate but decreased the GABA level, suggesting that zinc released into the synaptic cleft acts differentially on glutamatergic and GABAergic neurons in the CA3 region. The increase of GABA level by zinc was antagonized by 2,3-dioxo-6-nitro-1,2.3,4-tetrahydrobenzo(f)quinoxaline-7-sulphonamide (NBQX), an antagonist of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate receptors, but not affected by MK801, an antagonist of N-methyl-d-aspartate (NMDA) receptors, and verapamil, a blocker of voltage-dependent calcium channels. The present study suggests that zinc enhances GABA release via potentiation of AMPA/kainate receptors in the CA3 region, followed by a decrease in presynaptic glutamate release in the same region. Zinc seems to be an inhibitory neuromodulator of glutamate release. © 2003 Wiley-Liss, Inc.
http://www.plosone.org/article/info%3Ad ... ne.0055384Quote:
Zinc ions highly concentrate in hippocampus and play a key role in modulating spatial learning and memory. At a time when dietary fortification and supplementation of zinc have increased the zinc consuming level especially in the youth, the toxicity of zinc overdose on brain function was underestimated. In the present study, weaning ICR mice were given water supplemented with 15 ppm Zn (low dose), 60 ppm Zn (high dose) or normal lab water for 3 months, the behavior and brain zinc homeostasis were tested. Mice fed high dose of zinc showed hippocampus-dependent memory impairment. Unexpectedly, zinc deficiency, but not zinc overload was observed in hippocampus, especially in the mossy fiber-CA3 pyramid synapse. The expression levels of learning and memory related receptors and synaptic proteins such as NMDA-NR2A, NR2B, AMPA-GluR1, PSD-93 and PSD-95 were significantly decreased in hippocampus, with significant loss of dendritic spines. In keeping with these findings, high dose intake of zinc resulted in decreased hippocampal BDNF level and TrkB neurotrophic signaling. At last, increasing the brain zinc level directly by brain zinc injection induced BDNF expression, which was reversed by zinc chelating in vivo. These results indicate that zinc plays an important role in hippocampus-dependent learning and memory and BDNF expression, high dose supplementation of zinc induces specific zinc deficiency in hippocampus, which further impair learning and memory due to decreased availability of synaptic zinc and BDNF deficit.
http://link.springer.com/article/10.100 ... -y?LI=trueQuote:
Our results indicated that Zn treatment showed proconvulsant activity and increased BBB permeability, possibly changing prooxidant/antioxidant balance and neuronal excitability during seizures.
http://link.springer.com/article/10.100 ... -9?LI=trueQuote:
Zinc deficiency causes abnormal glucocorticoid secretion and increases depression-like behavior in animals. Neuropsychological symptoms are observed prior to the decrease in Zn2+ signal in the hippocampus under zinc deficiency. This paper summarizes that hippocampal Zn2+ signaling serves to maintain healthy brain and that glucocorticoid signaling, which is responsive to zinc homeostasis in the living body, is linked to the pathophysiology of depression.
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