Effect of magnesium on calcium-dependent brain function that prolongs ethanol-induced sleeping time in mice

Physical interactions driving the activation/inhibition of calcium/calmodulin dependent protein kinase II

CaMKII is a protein kinase whose function is regulated by the binding of the Calcium/Calmodulin complex (Ca²⁺/CaM). It is a major player in the Long Term Potentiation process where it acts as a molecular switch, oscillating between inhibited and active conformations. The mechanism for the switching is thought to be initiated by Ca²⁺/CaM binding, which allows the trans-phosphorylation of a subunit of CaMKII by a neighboring kinase, leading to the active state of the system. A combination of all-atom and coarse-grained MD simulations with free energy calculations, led us to reveal an interplay of electrostatic forces exerted by Ca²⁺/CaM on CaMKII, which initiate the activation process. The highly electrically charged Ca²⁺/CaM neutralizes basic regions in the linker domain of CaMKII, facilitating its opening and consequent activation. The emerging picture of CaMKII's behavior highlights the preponderance of electrostatic interactions, which are modulated by the presence of Ca²⁺/CaM and the phosphorylation of key sites.

Microfluidic Platform with In-Chip Electrophoresis Coupled to Mass Spectrometry for Monitoring Neurochemical Release from Nerve Cells

Chemical stimulus-induced neurotransmitter release from neuronal cells is well-documented. However, the dynamic changes in neurochemical release remain to be fully explored. In this work, a three-layered microfluidic chip was fabricated and evaluated for studying the dynamics of neurotransmitter release from PC-12 cells. The chip features integration of a nanoliter sized chamber for cell perfusion, pneumatic pressure valves for fluidic control, a microfluidic channel for electrophoretic separation, and a nanoelectrospray emitter for ionization in MS detection. Deploying this platform, a microchip electrophoresis-mass spectrometric method (MCE-MS) was developed to simultaneously quantify important neurotransmitters, including dopamine (DA), serotonin (5-HT), aspartic acid (Asp), and glutamic acid (Glu) without need for labeling or enrichment. Monitoring neurotransmitter release from PC-12 cells exposed to KCl (or alcohol) revealed that all four neurotransmitters investigated were released. Two release patterns were observed, one for the two monoamine neurotransmitters (i.e., DA and 5-HT) and another for the two amino acid neurotransmitters. Release dynamics for the two monoamine neurotransmitters was significantly different. The cells released DA most quickly and heavily in response to the stimulation. After exposure to the chemical stimulus for 4 min, the DA level in the perfusate from the cells was 86% lower than that at the beginning. Very interestingly, the cells started to release 5-HT in large quantities when they stopped releasing DA. These results suggest that DA and 5-HT are packaged into different vesicle pools and they are mobilized differently in response to chemical stimuli. The microfluidic platform proposed is proven useful for monitoring cellular release in biological studies.

Antidyskinetic effect of magnesium sulfate in MPTP-lesioned monkeys

The antiparkinsonian action of an NMDA receptor antagonist, magnesium sulfate (50, 100, and 200 mg/kg), alone and in association with levodopa was explored in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned parkinsonian and control rhesus monkeys. At the three doses tested, magnesium sulfate decreased levodopa-induced dyskinesia [cumulative dyskinetic scores after levodopa: 129 +/- 13; after levodopa and magnesium sulfate: 65 +/- 14 (50 mg/kg), P < 0.001; 64 +/- 10 (100 mg/kg), P < 0.001; 66 +/- 21 (200 mg/kg), P < 0.001, compared to levodopa administration alone]. These results show that magnesium sulfate importantly reduces levodopa-induced dyskinesia.

Intensification of the development of ethanol dependence in mice lacking dopamine D(3) receptor

The present study was designed to ascertain the role of dopamine D3 receptors in the development of physical dependence on ethanol using mice lacking the dopamine D3 receptor gene. The mutation eliminated the dopamine D3 receptor without any detectable changes in both dopamine D1 and D2 receptors. The ethanol-induced sleep time in dopamine D3 receptor knockout mice (D3-KO) was longer than that in wild-type mice. To examine the role of dopamine D3 receptors in the development of physical dependence on ethanol, two genotypes were chronically treated with 7% ethanol according to the liquid diet method. After the termination of ethanol treatment, severe withdrawal signs were observed in D3-KO mice as compared with wild-type mice. The present data suggest that the lack of dopamine D3 receptor genes in the mouse brain leads to the aggravation of the development of physical dependence on ethanol.

Opposite effects of calcium and magnesium on the central blood pressure regulation in the spontaneously hypertensive rats

The effects of intracerebroventricular administration of calcium or magnesium on the blood pressure regulation in the brain were investigated. The systolic blood pressure in spontaneously hypertensive rats (male, 13-week-old) was decreased by calcium chloride (100 microg/rat) and increased by magnesium chloride (20, 100 or 500 microg/rat). The depressor response induced by calcium was inhibited by magnesium chloride in a dose-dependent manner. Combining these results with those previously reported, it is suggested that magnesium inhibits the ability of calcium to reduce blood pressure through calmodulin- and dopamine-dependent functions in the brain.