Contrasting effects of 4-week inhalation exposure to pseudocumene or hemimellitene on sensitivity to amphetamine and propensity to amphetamine sensitization in the rat.
OBJECTIVE
Some data suggest that increased behavioural sensitivity to psychostimulants may develop after exposure to volatile chemicals in common use. The purpose of the present experiment was to find out whether and in what way inhalation exposure to pseudocumene (PS) or hemimellitene (HM) at low concentrations alters behavioural sensitivity to the psychostimulant amphetamine (AMPH), and propensity to develop behavioural sensitization to AMPH.


METHODS
Adult male Wistar rats were exposed 6 h/day, 5 days a week for 4 weeks to PS or HEM at 0, 25, 100 or 250 ppm. Behavioural sensitivity to AMPH was assessed by measuring locomotor activity of the animals in an open-field. Behavioural sensitization to AMPH was induced by a repeated AMPH treatment.


RESULTS
In rats exposed to HEM, the behavioural sensitivity to AMPH was increased, but remained unchanged in rats exposed to PS. The second testing revealed an augmented behavioural response to AMPH in control rats. In the HM exposed rats this augmenting was significantly more evident and in the PS exposed rats significantly less evident than in controls. For each of the two solvents, the concentration-effect relationship was nonlinear; out of the three concentrations used, 100 ppm was the most effective.


CONCLUSIONS
The results confirm that low-level inhalation exposure to trimethylbenzene isomers may induce behavioural sensitisation and/or increase the susceptibility of the animals to develop this state upon repeated psychostimulant treatment. They show, however, that HM and PS differ markedly in their ability to induce such alterations.
Lutz
Piotr
P
Department of Toxicology and Carcinogenesis, Toxicity Assement Laboratory, Nofer Institute of Occupational Medicine, Łódź, Poland. astra@imp.lodz.pl
Gralewicz
Sławomir
S
Wiaderna
Dorota
D
Swiercz
Radosław
R
Grzelińska
Zofia
Z
Majcherek
Wanda
W
D000661:Amphetamine / Q000633:toxicity*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001555:Benzene Derivatives / Q000633:toxicity*; D000697:Central Nervous System Stimulants / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D019570:Inhalation Exposure / Q000009:adverse effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D001555:Benzene Derivatives; D000697:Central Nervous System Stimulants; C010313:pseudocumene; C010179:hemimellitene; D000661:Amphetamine