Retrospectacle: A Neuroscience Blog

Huffing, or inhalant abuse, is a significant problem among young people and the homeless due to the habit being cheap and easily accessible legally. It involves the concentration and inhalation of chemicals that are found in many household cleaners, solvents, glue, paint, etc, which result in the person feeling inebriated or “high.” At higher concentrations these chemicals can induce nausea, psychosis, memory loss, emotional disturbances, or violent behavior. One of the most common ingredients in abused inhalants is toluene (think the smell of paint thinner), an aromatic hydrocarbon which causes intoxication similar to alcohol inebriation when inhaled. Abuse over long periods of time can cause irreversible brain damage, as is often evidenced in chronic huffers, as well as changes in brain regions associated with reward and addiction.

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Until recently, it was unknown what the exact effect of toluene was and how its abuse resulted in addiction (and eventually, damage). It was suspected that solvents like toluene acted on all brain regions rather than a specific one (like most drugs), but in 2002, neurologist Stephen Dewey demonstrated that toluene acts specifically on the reward pathways of the brain: the ventral tegmental area (VTA) and the nucleus accumbens (ACB). Other drugs, like cocaine and nicotine, activate dopamine neurons in the VTA, which stimulates the release of dopamine into the VTA and ACB. They found that toluene had a similar effect on the VTA but was unable to demonstrate that it stimulated the ACB, which led to speculation that toluene exerted effect by a method other than dopamine.

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However, a recent paper published in the January 2006 edition of Neuropsychopharmacology found that toluene also stimulated the ACB in a similar way to cocaine and nicotine. The authors (Riegel et al.) immersed rat brain slices in varying concentrations of toluene and found that lower concentrations were more potent: solutions of 1 micromolar and above didn’t activate the neurons, which explained why addicts prefer to administer in small amounts. They also injected small amounts of toluene into the brains of rats, and examined brain activation. They found that it stimulated the VTA (as previously found), but also dopamine was released into the ACB.

Comments

  1. #1 Abel Pharmboy
    February 10, 2007

    My buddy runs a course for pharmacy majors on substance abuse. I’ll never forget the lecturer who showed a brain scan (MRI, PET, I can’t recall) and said, “This is a perfectly normal brain for an 85-year-old woman.”

    The scan was from a 12-year-old girl who had been sniffing glue and solvents for about three years.

  2. #2 Lab Lemming
    February 11, 2007

    Is toluene the active ingredient in petrol (gasoline) sniffing?

  3. #3 Sock Puppet of the Great Satan
    February 13, 2007

    How come doing organic chemistry in a toluene solvent wasn’t more fun then?

    (Except for the time my lab partner heated toluene over an open flame)

  4. #4 lis
    March 9, 2010

    i have been sniff ing for years it has not affected me, i enjoy it i know how to sniff or inhale fume
    paint thinner and gasoline and xylene and diesel fuel supplements are my favorites i will continue

  5. #5 tyhara
    October 11, 2010

    i cant beleive that huffing is that harmful i mean when i was like 12 i tried it, and didnt reallly favor it. my just goes out to the people that are addicited

  6. #6 boka
    April 13, 2011

    i sniffed around 10 times so far…therz always a feeling of deja vu when i do it…even my frnds get that feeling…the high lasts for a short while but is much more intense than a marijuana high(even the best stuff)…n if i sleep after it n get up,i always get a feeling of bein born again…i quit doin it after one of my frnds strtd acting crazy

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