75A - PH - MEDICAL MARIJUANA - PROHIBIT

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Marijuana wreaks havoc on brain's memory cells 11:38 20 November 2006 NewScientist.com news service Roxanne hh.atnsi Smoking marijuana often causes temporary problems with memory and learning. Now researchers think they know why. The active ingredient in the drug, tetrahydrocannabinoid (THC), disrupts the way nerves fire in the brain's memory centre, a new study shows. David Robbe at Rutgers University in New Jersey, US, and colleagues gave rats an injected dose of THC, proportional to the amount inhaled. by a person smoking an average-sized. marijuana joint. The team monitored the drug's effect using wire probes placed in a memory centre i.n the animals' brains -the hippocampus. Th.e probes monitored the nerve impulses as they fired. Normally, cells ui hippocampus f re in sync, creating a current with. a total voltage of around 1 millivolt. But THC reduced the synchrony of the firing. The drug did not change the total number of firings produced, just their tendency to occur at the same time -and. this reduced the combined. output voltage of the nerve signals by about 50%. Abnormal firing occurs because THC binds to a receptor on the surface of the nerve cell., and so indirectly blocks the flow of current, Robbe believes. 1/ncore! Nerves need to signal in sync to send a powerful message within the brain, Robbe notes. He likens the process to an audience clapping together -rather than randomly - to make their desire for an encore performance known. Rats that had more synchronous nerve signaling in their brains performed better on a memory test, the team found. In this test, the animals had to choose whether to turn right or left in a T-shaped maze. In order to receive a treat, they had to turn in the direction opposite to the one they chose in their previous run. Normal rats accurately alternate their routes about 90% of the time. But rats given THC, which caused asynchronous nerve firing, chose a random direction. on each run, and so chose the correct route 50% of the time. The disruptive effect of THC wore aff within a few hours. Robbe says he hopes to Fnd out whether chronic exposure to the drug causes lasting effects on the hippocampus in rats. Scientists studying people have found that long-term marijuana users gradually become worse at ]earning and remembering things (see Pot-smoki.n~~your way to memory loss). Previous experiments have shown that THC can disrupt the signaling of nerve cells in a Petri dish. But Robbe says this is the first detailed account of what happens to memory cells in a live animal. He adds that the new findings help explain why people high on marijuana sometime lose their train of thought in mid- sentence, forgetting what they were saying. Journal reference: Nature Neuroscience (DOI: 10.1038/nn1801} Source: http://www.newscientist.com/channel/health/dn].0607-mat~ijuatla-wreaks-havoc- on -brains-memory-c el ls.html Marijuana may cause pregnancies to fail. 22:00 O1 August 2006 NewScientist.com news service Michael Day Smoking marijuana at the time of conception could cause pregnancies to fail, new research in mice suggests. The same problem may occur as a result of taking the slimming drug, rimonabant. The wan~ings come from embryologists who have discovered key factors that govern an embryo's chances of successful implantation. A IS 75A-89