Control of E-S Potentiation at two different sites in the dendro-somatic axis

Abstract

1 2 EPSP-Spike (E-S) Potentiation occurs alongside synaptic Long-Term Potentiation 3 (LTP), both triggered by high-frequency synaptic stimulation (HFS). In this study, we 4 confirm the earlier findings that E-S potentiation appears to be prevented by prior 5 reduction of GABAA receptor-mediated inhibitory synaptic transmission. However, we 6 demonstrate that this is a result of an occlusion of E-S potentiation, not a block. E-S 7 potentiation and GABAA antagonism each saturate postsynaptic action potential 8 discharge, but E-S potentiation can still be induced by high frequency activation of 9 synapses, even in the presence of pharmacological GABAA blockade. These results 10 suggest that GABAA blockers/antagonists and E-S potentiation share an expression 11 mechanism, namely the reduction of GABAA-mediated synaptic inhibition. We also 12 assayed changes in the electrical coupling between dendrite and soma, and were 13 surprised to find that this coupling is decreased following HFS, a change that would 14 oppose E-S potentiation. This decrease in dendritic-soma electrical coupling (D-S 15 coupling) was induced through the action of GABAB receptors, but not maintained or 16 expressed via the activity of these receptors. These data all together suggest that there 17 are two distinct and opposing changes that occur as a result of HFS: 1) A decrease in 18 passive dendro-somatic electrical coupling, and 2), an increase in coupling between the 19 somatic EPSP and action potential generation. These two opposing influences may 20 function as a homeostatic mechanism to balance the excitatory/inhibitory relationship 21 between primary neurons and interneurons, and may represent a separate mechanism 22 by which feedback and feed-forward synaptic inhibition can influence E-S coupling in 23 opposite directions. 24 25 26

Chemical bonding and valence states in Au-associated host minerals

“…Quartz is soluble at pHs both above and below 7 (neutral) and is thus soluble in both acidic and basic solution environments with solubility minima at a pH of about 7 [41]. In a hydrothermal system, Au associated with SiO 2 is generally transported as chloride [42], sul de (Au(HS) 2-), and thiosulfate (Au(S 2 O 3 ) + ) components [43,44] that are either acidic for chlorides or basic for sul des. In the absence of dissolved acid gas such as CO 2 , the mineral forming solution in the environment boils, resulting in a change in temperature, pressure, and composition [41].…”