Abstract: Feeding behaviors can be influenced by a multitude of factors including demographics and socioeconomic status, biological tendencies, nutritional knowledge, food preference, and portion size (Scaglioni et al., 2018). As the intersectionality of these factors have important implications for prevention and treatment of obesity, it is important to investigate the nature by which feeding behaviors may be altered. Sigma 1 receptors have been investigated for their involvement in learning, rewarding and motivational processes. PD144418, a potent and selective sigma 1 ligand exhibiting a high affinity and selectivity for sigma 1 receptors, has been found to produce a dose-dependent attenuation of locomotor activity induced by cocaine and methamphetamine. However, it was unknown as to whether PD144418 could alter the motivational effort of food-reinforced operant behavior. The current talk will focus on examining the effects of PD144418 on motivational effort of food-reinforced operant behavior, as well as variables of sex differences and energy deficit.