Volatile solvents such as toluene, benzene and trichloroethane are widely distributed in a variety of products encountered in both industrial and home settings. These include glues, thinners, rubber cements, aerosol sprays, nail polish removers, correction fluid and dry cleaning solvents. Although the occupational hazards of exposure to these solvents have been previously examined in a variety of toxicological studies, the cellular and molecular sites of action that account for their intoxicating effects are virtually unknown. Surveys of drug use show that a significant percentage of the population has used volatile solvents for their intoxicating properties and such use is especially prevalent among adolescents and teens who may have easy access to these products. Previous behavioral studies show that toluene and other abused volatile solvents display actions similar to that observed for CNS depressants such as ethanol, barbiturates, benzodiazepines, and anesthetics. Thus, we hypothesize that abused solvents, like other CNS depressants, may exert some of its neurobehavioral effects by altering the function of specific ion channels that are involved in mediating and modulating neuronal transmission. We have generated data to support this hypothesis and have demonstrated that toluene and other volatile solvents inhibit the function of recombinant and native NMDA and acetylcholine receptors expressed in oocytes and cultured neurons. This inhibition was dose-dependent and was influenced by the subunit composition expressed. In contrast to ethanol, toluene had negligible effects on currents mediated by non-NMDA receptors or on G-protein coupled potassium channels. These results suggest that abused solvents may show greater selectivity than alcohol with respect to their ability to modulate the activity of neuronal ion channels. Studies outlined in this proposal will test this hypothesis by determining the sensitivity of recombinant and native ion channels to toluene and other volatile solvents that are subject to abuse. Two-electrode voltage-clamp and patch-clamp electrophysiology will be used to analyze the solvent sensitivity of recombinant ionotropic receptors expressed in oocytes and HEK cells. The molecular sites of action for toluene will be explored by testing whether sites known to regulate the alcohol/anesthetic sensitivity of these channels also regulate solvent sensitivity. Finally, the relevance of the findings obtained in recombinant receptor systems will be assessed by measuring the effects of toluene and other abused solvents on ion channels expressed in cultured brain neurons using whole-cell patch clamp and calcium imaging. Results obtained from these studies outlined are expected to greatly expand our knowledge of the cellular and molecular targets of these important drugs of abuse.
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