Toluene increases acute thermonociception in mice

Toluene is an abused solvent widely used in several commercial products. Re cent evidence indicates that this solvent is a non-competitive inhibitor of NMDA receptors. Since NMDA receptors have been implicated in pain, this pa per describes studies of the effects of increasing concentrations of inhale d toluene on nociception. Swiss Webster mice were exposed to toluene (500-8 000 ppm) in static exposure chambers for 30 min. After completing the expos ure period, animals were tested for nociception using the hot plate test. T oluene dose-dependently increased nociception as reflected by shorter laten cies for the reflex, paw-lick and escape responses in toluene-treated mice with respect to their controls (animals exposed to air). In order to determ ine the possible role of opioids in this response, morphine (1-10 mg/kg) wa s injected before toluene inhalation. Toluene was not able to block morphin e-induced antinocieption, however. it produced a shift of the morphine dose -response curve to lower effects. suggesting a physiological antagonism. No potentiation was seen when toluene was administered in combination with na loxone. Present results suggest that toluene increases nociception via neur otransmitter systems others than the glutamatergic. (C) 2001 Elsevier Scien ce B.V. All rights reserved.