A HIGH TO REMEMBER

Marijuana Chemicals May Benefit Those With Alzheimer's

There has been a long debate over legalization, but is marijuana a
good thing? Recent studies show that while certain chemicals in
marijuana damage adolescent brains, they are beneficial to adults,
especially those with diseases such as Alzheimer's.

Veronica Campbell, a neuropharmacologist from Trinity College in
Dublin, says that marijuana truly works both ways.

A recent study conducted by Campbell and her team used the
tetrahydrocannabinol (THC) chemical from marijuana-the chemical
responsible for the high-and tested it on newborn, adolescent, and
adult rats. In the newborn and developing adolescent rats, THC
exposure resulted in brain cell death. In contrast, it was not as
detrimental to neurons in adult rats.

Why does this happen? "We don't know," said Campbell in an interview
with Scientific American Mind. "It's still being investigated."

"The most psychoactive cannabinoid chemical [in marijuana] is
tetrahydrocannabinol," explains Dr. Jeffrey Henderson, director of
Murine Imaging and Histology at U of T. "THC receptors in the brain
are concentrated in the hippocampus (the part of the brain associated
with long-term memory), amygdala (associated with processing the
memory of emotional reactions), and the cerebellum (associated with
motor controls and sensory perception), which are all affected when
one gets high." Henderson points out, "the most clearly confirmed
medical benefits of marijuana are anti-nausea, enhanced appetite, and
pain decrease, [yet] long term usage may still be toxic to the brain."

Campbell's recent study highlighted the overall effects of THC on the
human brain. The "slaughter" of young neurons by THC, as Campbell
calls it, could explain why some who smoked pot while pregnant have
children with cognitive impairment and why some adolescent marijuana
users show brain damage in their still-developing neural circuits.

As neurons mature and cells age, their biochemistry also changes.
Endocannabinoids (the chemicals that regulate important functions in
the brain, such as thought and perception) start to shift and regulate
different functions. These endocannabinoids appear to assist in the
survival of neurons in adults. This is extremely important in patients
with Alzheimer's disease, as it improves mental function by decreasing
levels of the neurotransmitter acetylcholine, which contributes to
memory loss. It also suppresses the toxic effects of the abeta
protein, which kills brain cells.

Henderson explains, "THC acts by mimicking the actions of
endocannabinoids, which normally exist in our brain. All of these
agents work by suppressing a part of the normal inhibitory signals in
our brains."

"While there is some evidence to suggest that THC derivatives may
reduce Abeta aggregates in culture, a number of the mechanistic
aspects of how this occurs are presently unclear. There is evidence to
suggest that THC derivative competitively stalls the enzyme
acetylcholinesterase, as well as prevents Abeta aggregation, a key
pathological marker of Alzheimer's disease," says Henderson.

Before we start encouraging Alzheimer's patients to smoke up, Campbell
told Scientific American Mind that "the beneficial effects of the THC
are in much lower concentrations of the chemical that are found in the
actual plant that people use to get high."

A new challenge is to isolate the important chemicals of cannabinoids
in marijuana and see which ones, including the THC molecule, have a
protective effect on neurons.

In small doses, there are some components of marijuana that when
cultivated properly, could be potentially lifesaving. Overall, raw
marijuana is still harmful when used over long periods of time.

Numerous studies are still being conducted in this area, so it looks
like smoking a bowl isn't the answer quite yet.