Chloride ion conduction

AHopregnanolone and similar A-ring-reduced pregnanes potentiate GABA effects at these receptors. These steroids mimic the effects of the benzodiazepines, changing chloride ion conductance and producing sedative and hypnotic behavioral effects (276,277). Neuroactive steroids can be therapeutically useful as anticonvulsants, anxiolytics, or anesthetics (qv) (see also Hypnotics, sedatives, anticonvulsants, and anxiolytics). 

Several classes of pharmacologic agents are available for insomnia. Barbiturates are the oldest agents that have been used for insomnia and include pentobarbital, secobarbital, and amobarbital. Barbiturates are currently not recommended because of their high abuse potential (due to rapid development of tolerance) and lethal potential in overdose situations. Barbiturates potentiate the GABAergic-induced increase in chloride ion conductance at low doses, and at high doses they depress calcium-dependent action potentials. Caution should be exercised in patients with marked renal or liver dysfunction, severe respiratory disease, suicidal tendencies, or history of alcohol/drug abuse. 

Hydrochloric acid is secreted by parietal cells via H, K -ATPase pumps (proton pumps), of which there are more than one million per cell. The H, K -ATPase pumps utilize the phosphorylation of ATP to exchange water-solvated protons (protonated water, hydroxonium ion, H30 ) for potassium ions. In conjunction with parallel potassium and chloride ion conductances, this ATPase is responsible for the secretion of hydrochloric acid into the secretory canaliculus of the parietal cell, the enclosed space reaching a pH of near 1.0 (Rabon Reuben 1990). In the resting parietal cell, these pumps reside within the membranes of vesicles in the cell cytoplasm. When activated by histamine and gastrin, the parietal cells alter their shape and the vesicles merge with the outer cell membrane to form secretory canaliculi. 

E. facilitating GABA-mediated increases in chloride ion conductance... 

Activation of both GAB and glycine receptors present on neurons in the spinal cord leads to membrane hyperpolarization via increases in chloride ion conductance. In the case of glycine, its inhibitory action at the level of the spinal cord is opposed by strychnine, which acts as a glycine receptor antagonist. The answer is (D). 

This neurotransmitter, located in the spinal cord, is inhibitory to motor neurons via an increase in chloride ion conductance... 

Independently, Hua and Flood synthesized a light-active aryl-triazole foldamer (42, Fig. 22) which has two azobenzene units on each end [54]. When the azobenzene units are photoisomerized from trans to cis with UV (365 nm) irradiation, the foldamer loses two of its three aromatic n-n interactions that were being employed to stabilize the hehcally folded form. Therefore, UV irradiation destabilizes the folded helix in favor of the unfolded random-coil conformation. The folded conformation could be reinstated by irradiation with visible light (436 nm). In solution, the foldamer binds with chloride in its trans isomer (/sTa = 3,000 MeCN) and releases chloride in the cis isomer (K = 380 M ). On account of the fact that free chloride ions conduct electricity through solution better than receptor-bound chloride, the anion binding-release cycle was observed by conductivity measurements. Consistently, a 1 1 solution of 42 and TBACl (MeCN) showed increased conductivity under UV light and decreased conductivity under Vis light. 

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