Developmental Exposure to Concentrated Ambient Particles and Preference for Immediate Reward in Mice

Joshua L. Allen,¹ Katherine Conrad,¹ Günter Oberdörster,¹ Carl J. Johnston,² Brianna Sleezer,¹ and Deborah A. Cory-Slechta¹

¹Department of Environmental Medicine, and ²Department of Pediatrics, University of Rochester School of Medicine, Rochester, New York, USA


Abstract

Background: Recent epidemiological studies indicate negative associations between a diverse group of air pollutants and cognitive functioning in children and adults, and aspects of attention deficit in children. Neuroinflammation and oxidative stress are two putative biological mechanisms by which air pollutants may adversely affect the brain.


Objectives: We sought to determine whether exposure to concentrated ambient particulate matter (CAPS) during the first 2 weeks of life, alone or again in adulthood, could alter responding for delayed reward, a critical component of human decision making. Greater preference for immediate reward has been implicated as a component of several psychiatric disorders, addiction, obesity, and attention deficit.


Methods: C57BL/6J mice were exposed to ultrafine particles (< 100 nm in aerodynamic diameter; CAPS) using the Harvard University Concentrated Ambient Particle System (HUCAPS) or filtered air in the postnatal period (days 4–7 and 10–13) with and without adult exposure over days 56–60. In adulthood, delay behavior was assessed using a fixed-ratio waiting-for-reward (FR wait) paradigm in which 25 responses (FR25) were required to initiate the waiting-for-reward component during which mice obtained “free” sucrose pellets with the stipulation that these “free” pellets were delivered at increasing delay intervals.


Results: Coupled with increased FR response rates, mice exposed to postnatal CAPS displayed increased FR resets that reinstated short delays, indicating a preference for shorter delays, despite the added response cost of the FR25. No associated changes in locomotor activity were observed.


Conclusions: Postnatal CAPS exposure produces an enhanced bias towards immediate rewards, a risk factor for several central nervous system (CNS) disorders. This enhancement does not appear to be the result of hyperactivity. The findings underscore the need for further evaluation of air pollution effects on the CNS and its potential contribution to CNS diseases and disorders.


Key words: air pollution, ambient particles, attention deficit, behavior, delay of reward, fixed-ratio waiting-for-reward, impulsivity, particulate matter, ultrafine particles. 


Environ Health Perspect 121:32–38 (2013). http://dx.doi.org/10.1289/ehp.1205505 [Online 11 October 2012]


Address correspondence to D.A. Cory-Slechta, 601 Elmwood Ave., Box EHSC/Room 2-6812, Department of Environmental Medicine, University of Rochester School of Medicine, Rochester, NY 14642 USA. Telephone: (585) 275-7060. Fax: (585) 256-2591. E-mail: deborah_cory-slechta@urmc.rochester.edu


Supplemental Material is available online (http://dx.doi.org/10.1289/ehp.1205505).


We thank P. Mercer-Wade, N. Corson, A. Elder, and R. Gelein for expert assistance with the Harvard University Concentrated Ambient Particle System exposures. 


This work was supported by ES012105 (D.A.C.-S.) ES001247 [National Institute of Environmental Health Sciences (NIEHS) Center of Excellence] and T32 ES007026 (NIEHS Toxicology training grant).


The authors declare they have no actual or potential competing financial interests.


Received 22 May 2012; Accepted 11 October 2012; Online 11 October 2012.