By Anne Harding
NEW YORK (Reuters Health) – Teens who experiment with
marijuana may be making themselves more vulnerable to heroin
addiction later in life, if the findings from experiments with
rats are any indication.
“Cannabis has very long-term, enduring effects on the
brain,” Dr. Yasmin Hurd of the Mount Sinai School of Medicine
in New York, the study’s lead author, told Reuters Health in an
interview.
Whether or not trying marijuana is a ‘gateway’ to use of
so-called harder drugs like heroin and cocaine has been hotly
debated, she and her colleagues note in the journal
Neuropsychopharmacology.
To investigate whether pot smoking could cause brain
changes that might predispose an individual to later drug use,
Hurd and her team looked at rats exposed to the active
ingredient in marijuana, THC, during a developmental period
similar to human adolescence. To mimic the relatively small
amount used by most teens experimenting with pot, the rodents
received periodic, small doses of THC.
As young adults, the animals were fitted with catheters
that allowed them to self-administer heroin. The researchers
compared the amount and frequency of their drug use with that
of rats that had not been given THC previously.
The THC-exposed rats were more sensitive to the effects of
heroin, the researchers found, and also consistently used
larger amounts of the drug.
The researchers also found that the THC-exposed rats showed
disturbances in the brain’s endogenous opioid system, which is
often popularly referred to as the “reward system” of the brain
and, in humans, is involved in experiencing pleasure.
“I was really surprised at how specific and enduring the
effects of cannabis were,” Hurd said.
She and her colleagues conclude: “The current findings
provide direct evidence in support of the gateway hypothesis
that adolescent cannabis exposure contributes to greater heroin
intake in adulthood.”
SOURCE: Neuropsychopharmacology
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