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Marijuana against Alzheimer’s disease?

Oct. 18, 2006
Courtesy Ohio State University 
and World Science staff
Updated Oct. 19

A rat study sug­gests chem­i­cals in ma­ri­jua­na may slow the mem­o­ry loss of Alzheimer’s dis­ease, re­search­ers say.

Added to signs that pot-smoking vet­er­ans of the 1960s and 1970s drug cul­ture rare­ly de­vel­op the dev­as­tat­ing con­di­tion, they add, the find­ings could point to new av­e­nues for Alz­hei­m­er’s treat­ment.

Ma­ri­jua­na may have some anti-Alz­hei­m­er's dis­ease ef­fects, re­search­ers say. (Im­age cour­te­sy Cal­i­for­nia Na­tion­al Guard Coun­ter­drug Task Force )
Re­search­ers want to de­vel­op a drug with ma­ri­jua­na’s ben­e­fi­cial pro­p­er­ties, but with­out the mind-al­t­er­ing ef­fects, said Ga­ry Wenk of Ohio State Uni­ver­si­ty in Co­lum­bus, Ohio, one of the sci­en­tists.

The key to ma­ri­jua­na’s ben­e­fit, he ad­ded, may be its strong ef­fect against chron­ic in­flam­ma­tion, wide­ly be­lieved to be a ma­jor fac­tor in Alz­hei­m­er’s. 

“In­flam­ma­tion in the brain is part of ag­ing,” he said. “It hap­pens to al­most all of us... But in some cases, this in­flam­ma­tion gets out of hand and causes se­ri­ous da­m­age.”

Treat­ment with a syn­thet­ic com­pound si­m­i­lar to ma­ri­jua­na re­duced in­flam­ma­tion in old­er rats and made them “smart­er,” he added. “The com­pound sub­stan­tial­ly im­proved the mem­o­ries of the old­er rats, [who] were able to hold on to key de­tails of a spe­cif­ic task. Un­treat­ed old­er rats, on the oth­er hand, were not.”

His team pre­sented pre­sented its find­ings Oct. 18 in At­lan­ta at the an­nu­al meeting of the So­ci­e­ty for Neu­ro­science. A si­m­i­lar, Spa­n­ish stu­dy pub­lished in the Jour­nal of Neu­ro­science ear­ly last year found that rats in­jected with a can­nabi­noid, a syn­thet­ic ver­sion of the mar­i­jua­na’s ac­tive in­gre­di­ent, suf­fered less men­tal de­cline in ar­ti­fi­cial­ly in­duced Alzheimer’s dis­ease than others.

Wenk’s team treated young and old rats with WIN-55212-2, or simp­ly WIN, a syn­thet­ic drug si­m­i­lar to ma­ri­jua­na. While the com­pound im­proved mem­o­ry and helped to con­trol in­flam­ma­tion, it’s is not a can­di­date for use in hu­mans be­cause it still con­tains sub­stances that could trig­ger a high, Wenk added.

“We don’t use ma­ri­jua­na in our ex­per­i­ments be­cause we’re try­ing to find a com­pound that is­n’t psy­cho­ac­tive,” Wenk said. “And us­ing syn­thet­ic com­pounds may even­tu­al­ly help us to sep­a­rate the ben­e­fi­cial ef­fects from the psy­cho­ac­tive ef­fects.”

The re­search­ers in­sert­ed a small tube in­to the brain of each rat to pe­ri­od­i­cal in­fuse lipopolysac­cha­ride, a ma­te­ri­al that stim­u­lates an im­mune re­ac­tion that mim­ics the in­flam­ma­tion of Alz­hei­m­er’s.

Some of the rats were al­so treated with WIN dai­ly for the three weeks dur­ing which in­fu­sions took place.

The an­i­mals were sub­jected to a mem­o­ry test dur­ing the third week. They nav­i­gat­ed a wa­ter maze that re­quires find­ing an es­cape plat­form hid­den just be­low the sur­face of opaque wa­ter. The rats were giv­en sev­er­al op­por­tu­ni­t over three days to ac­cli­mate to the wa­ter maze. On the fourth day, the re­search­ers timed how quick­ly each rat found the plat­form.

“The maze task is sen­si­tive to mem­o­ry im­pair­ment and al­so to ag­ing,” Wenk said. “Old rats tend to be pret­ty bad at nav­i­gat­ing the maze. It’s kind of like an eld­er­ly per­son try­ing to find his way around a house that he’s not fa­mil­iar with.”

The com­pound “sig­nif­i­cantly im­proved the old­er rats’ mem­o­ries,” Wenk said. “They found the plat­form faster, sug­gest­ing that they were less apt to for­get key in­for­ma­tion for this task. It’s a pret­ty good pre­dic­tion of how a hu­man would re­spond to this drug.”

Alzheimer’s, a dev­as­tat­ing, pro­gres­sive de­gen­er­a­tion of the brain es­ti­mat­ed to af­fect 4 mil­lion Amer­i­cans, typ­i­cal­ly starts in the 40s or 50s with mem­o­ry difficul­ties. This tends to lead to im­paired thought and speech, and even­tu­al­ly to­tal help­less­ness.

* * *

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A rat study suggests chemicals in marijuana may slow the memory loss of Alzheimer’s disease, researchers say. Added to signs that pot-smoking veterans of the 1960s and 1970s drug culture rarely develop the devastating condition, researchers say, the findings could point to new avenues for Alzheimer’s prevention. Researchers want to develop a drug with marijuana’s beneficial properties, but without its psychoactive effects, said Gary Wenk of Ohio State University in Columbus, Ohio, one of the scientists. The key to marijuana’s benefit, he added, may be its strong effect against chronic inflammation, believed to be a major factor in Alzheimer’s. “Inflammation in the brain is part of aging,” he said. “It happens to almost all of us as we age. But in some cases, this inflammation gets out of hand and causes serious damage.” Treatment with a synthetic compound similar to marijuana reduced inflammation in older rats and made them “smarter,” he added. “The compound substantially improved the memories of the older rats, [who] were able to hold on to key details of a specific task. Untreated older rats, on the other hand, were not.” His team presented presented its findings Oct. 18 in Atlanta at the annual Society for Neuroscience meeting. Wenk’s colleagues treated young and old rats with WIN-55212-2, or simply WIN, a synthetic drug similar to marijuana. While the compound improved memory and helped to control inflammation, it is not a candidate for use in humans because it still contains substances that could trigger a high, Wenk added. “We don’t use marijuana in our experiments because we’re trying to find a compound that isn’t psychoactive,” Wenk said. “And using synthetic compounds may eventually help us to separate the beneficial effects from the psychoactive effects.” The researchers inserted a small tube into the brain of each rat to periodically infuse lipopolysaccharide, a material that stimulates an immune reaction that mimics the inflammation of Alzheimer’s. Some of the rats were also treated with WIN daily for the three weeks during which infusions took place. The animals were subjected to a memory test during the third week. They navigated a water maze that requires finding an escape platform hidden just below the surface of opaque water. The rats were given several opportunities over three days to acclimate to the water maze. On the fourth day, the researchers timed how quickly each rat found the platform. “The maze task is sensitive to memory impairment and also to aging,” Wenk said. “Old rats tend to be pretty bad at navigating the maze. It’s kind of like an elderly person trying to find his way around a house that he’s not familiar with.” The compound “significantly improved the older rats’ memories,” Wenk said. “They found the platform faster, suggesting that they were less apt to forget key information for this task. It’s a pretty good prediction of how a human would respond to this drug.”