1. Department of Psychology, University of Kentucky, College of Arts and Sciences, Lexington, Kentucky, USA;2. Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, Kentucky, USA
Abstract:
The attribution of incentive salience to reward‐predictive stimuli has been shown to be associated with substance abuse‐like behavior such as increased drug taking. Evidence suggests that glutamate neurotransmission and sequential N‐methyl‐D‐aspartate (NMDA) activation are involved in the attribution of incentive salience. Here, we further explore the role of second‐by‐second glutamate neurotransmission in the attribution of incentive salience to reward‐predictive stimuli by measuring sign‐tracking behavior during a Pavlovian conditioned approach procedure using ceramic‐based microelectrode arrays configured for sensitive measures of extracellular glutamate in awake behaving Sprague‐Dawley rats. Specifically, we show that there is an increase in extracellular glutamate levels in the prelimbic cortex (PrL) and the nucleus accumbens core (NAcC) during sign‐tracking behavior to a food‐predictive conditioned stimulus (CS+) compared to the presentation of a non‐predictive conditioned stimulus (CS?). Furthermore, the results indicate greater increases in extracellular glutamate levels in the PrL compared to NAcC in response to the CS+, including differences in glutamate release and signal decay. Taken together, the present research suggests that there is differential glutamate signaling in the NAcC and PrL during sign‐tracking behavior to a food‐predictive CS+.
