Effect of environmental enrichment components on memory impairment and addictive behavior induced by toluene

[Speaker] Nayeli Paez-Martinez:1,2
[Co-author] Ricardo Mosco-Aquino:2,3, Roberto E Mercadillo:3,4
1:Seccion de Posgrado e Investigacion, School of Medicine. Instituto Politecnico Nacional, Mexico, 2:Laboratorio Integrativo para el Estudio de Sustancias Inhalables Adictivas. Instituto Nacional de Psiquiatria. Ciudad de Mexico., Mexico, 3:Area de Neurociencias, Departamento de Biologia de la Reproduccion. Universidad Autonoma Metropolitana-Iztapalapa. Ciudad de Mexico., Mexico, 4:Consejo Nacional de Ciencia y Tecnologia. Ciudad de Mexico, Mexico

Background. Toluene is the main chemical component in volatile substances used to induce psychoactive effects; its abuse produces memory impairment and addictive behavior. Previous preclinical models accomplished in our lab reveal that environmental enrichment (EE) may reverse some of these cognitive and behavioral alterations induced by toluene; however, it is unclear which of the components shaping the enrichment are responsible for those reversal effects. Our objective in this study was to evaluate and to compare the reversal effect of a complete environmental enrichment (CEE), motor stimulation (ME), and cognitive stimulation (CE) over the memory impairment and addictive behavior produced by toluene.
Methods. 90 Male Swiss webster mice (5 weeks age) were exposed to toluene vapors (0 or 4000 ppm), 30 min/day, 4 weeks. Subsequently, experimental subjects were grouped (n= 15) and housed during 4 more weeks on a CEE (shaped by wheels for voluntary exercise, tunnels and toys), a ME environment (only wheels for voluntary exercise), and a CE environment (only tunnels and toys). Control subjects (n= 45) were housed on standard conditions without stimulation. All subjects were assessed at the end of the housing exposure by conducting the object recognition task to evaluate memory, and the expression phase of the locomotor sensitization test to evaluate addictive behavior.
Results. The three experimental conditions (CEE, ME, CE) equivalently produced improvements on memory in all the subjects. Concerning the expression of addictive behavior, the three experimental conditions reduced locomotor activity but in different degree according the following order: CEE > ME > CE. Subjects housed on standard conditions presented the typical impairments on memory and expression of addictive behavior previously reported in association to toluene exposures.
Conclusion. EE's components have differentiated effects on toluene induced cognitive and behavioral alterations. The more effective rescue is provided by CEE, although motor and cognitive stimulation still produce partial cognitive and behavioral results. Withdrawal from toluene exposure is not an enough condition to recover cognitive and behavioral abilities. Our results offer a promissory and an accurate perspective to consider preclinical findings on therapeutic strategies for inhalant abuse in human populations.

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