Proteins linked to synaptic 'memory.'Proteins linked to synaptic synaptic /syn·ap·tic/ (si-nap´tik) 1. pertaining to or affecting a synapse. 2. pertaining to synapsis. syn·ap·tic adj. Of or relating to synapsis or a synapse. 'memory' Several investigators have noted that when individual neurons are given brief but intense bursts of high-frequency electrical stimulation, their electrical properties change and chemical transmissions across their connecting synapses increase for hours or days. This process, known as long-term potentiation and readily demonstrated in cells from a small brain structure called the hippocampus hippocampus fabulous marine creature; half fish, half horse. [Rom. Myth. and Art: Hall, 154] See : Monsters , may play a crucial role in the formation of memories. Stanford University School of Medicine Stanford University School of Medicine is affiliated with Stanford University and is located at Stanford University Medical Center in Stanford, California, adjacent to Palo Alto and Menlo Park. researchers report that the protein kinases -- several related substances involved in the regulation of chemical messengers and their receptors in neurons -- are key to the chemical mechanisms underlying long-term potentiation. Physiologist Roberto Malinow and his colleagues used two protein-kinase-inhibiting substances to study long-term potentiation in rat hippocampus cells. When either of the two substances -- sphingosine sphingosine /sphin·go·sine/ (sfing´go-sen) a long-chain, monounsaturated, aliphatic amino alcohol found in sphingolipids. sphin·go·sine n. or a synthetic compound called H7 -- is applied to hippocampal hip·po·cam·pus n. pl. hip·po·cam·pi A ridge in the floor of each lateral ventricle of the brain that consists mainly of gray matter and has a central role in memory processes. synapses shortly before high-frequency stimulation, long-term potentiation is blocked, the investigators note in the Oct. 27 NATURE. But sphingosine, which subdues the activity of two protein kinases, does not dampen the increased electrical charge associated with long-term potentiation when applied immediately after the stimulation. In contrast, H7 -- which interferes with the activity of additional protein kinases -- inhibits long-term potentiation even after high-frequency stimulation clearly establishes the effect. Surprisingly, the researchers add, when H7 degrades after several hours, there is an almost complete recovery of the original long-term potentiation. The results indicate a "sphingosine-sensitive process" is critical to induce long-term potentiation, the researchers suggest, whereas an unidentified protein kinase affected by H7 is crucial for its maintenance. Unfortunately, writes biologist Mary B. Kennedy of the California Institute of Technology California Institute of Technology, at Pasadena, Calif.; originally for men, became coeducational in 1970; founded 1891 as Throop Polytechnic Institute; called Throop College of Technology, 1913–20. in Pasadena in an accompanying comment, both sphingosine and H7 are insufficiently specific to distinguish among the several known protein kinases. Even if the critical protein kinases are pinned down, says Kennedy, much remains to be explained about long-term potentiation. There are now indications that one class of postsynaptic postsynaptic /post·sy·nap·tic/ (-si-nap´tik) distal to or occurring beyond a synapse. post·syn·ap·tic adj. Situated behind or occurring after a synapse. receptors involved in this process releases a chemical messenger able to travel back and forth across the synapse synapse (sĭn`ăps), junction between various signal-transmitter cells, either between two neurons or between a neuron and a muscle or gland. A nerve impulse reaches the synapse through the axon, or transmitting end, of a nerve cell, or neuron. . "Other entirely new messenger systems may be awaiting discovery," Kennedy concludes. |
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