Re­searchers ex­am­ine how brain cells com­mu­ni­cate

The Hamilton Spectator - - HEALTH - LAURAN NEERGAARD

WASH­ING­TON — The brain’s nerve cells com­mu­ni­cate by fir­ing mes­sages to each other through junc­tions called synapses, and prob­lems with those con­nec­tions are linked to dis­or­ders like Alzheimer’s and epilepsy. Now Yale Univer­sity re­searchers have de­vel­oped a way to pic­ture synapses in liv­ing brains.

The ex­per­i­men­tal tech­nique, us­ing PET scans, raises the pos­si­bil­ity of mon­i­tor­ing sy­napse func­tion in some com­mon dis­eases.

A healthy hu­man brain har­bours tril­lions of synapses, a num­ber that changes over a life­time. Early in life, the brain “prunes” the many synapses be­tween neu­rons so the right num­ber is in each re­gion, a process that can go wrong in dis­or­ders such as autism or schizophre­nia. Changes in the den­sity of synapses may sig­nal where epilepsy seizures orig­i­nate. Later in life, sy­napse loss is as­so­ci­ated with Alzheimer’s dis­ease. But mea­sur­ing synapses has re­quired au­top­sies, or at­tempts dur­ing brain surgery.

To find a non-in­va­sive ap­proach, the Yale-led team de­vel­oped a ra­dioac­tive com­pound, called a tracer, that is in­jected into the body and binds with a par­tic­u­lar pro­tein that is found in the brain’s synapses. Dur­ing a PET scan, those synapses ap­pear lit up against dark, synapse­free areas of the brain.

Animal test­ing con­firmed the tracer was tar­get­ing synapses. Re­searchers then mapped the den­sity of synapses in the brains of 10 healthy vol­un­teers and three pa­tients with epilepsy. Com­pared to the healthy brains, the tech­nique re­vealed lost synapses in the epilepsy-af­fected re­gions of those pa­tients’ brains, re­searchers re­ported Wed­nes­day in the jour­nal Science Trans­la­tional Medicine.

“This work rep­re­sents a break­through in the abil­ity to study an im­por­tant process in the brain that is not only part of nor­mal brain de­vel­op­ment but that also may be in­volved in sev­eral neu­ropsy­chi­atric dis­eases,” said Dr. Peter Her­scov­itch, who di­rects PET scan­ning at the Na­tional In­sti­tutes of Health’s Clin­i­cal Cen­ter and wasn’t in­volved in the re­search.

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