Association for Behavior Analysis International

Cannabidiol (CBD) is one of the major centrally active phytocannabinoid components of cannabis, and has been approved by the FDA only for the treatment of two rare seizure disorders. However, CBD has been touted as a potential treatment for anxiety in place of more traditional pharmacological treatments like benzodiazepines. Although there is some evidence of anxiolytic effects of CBD, its suitability as a substitute for benzodiazepines is unknown. This experiment was designed to assess to what extent CBD shares interoceptive discriminative-stimulus properties with the anxiolytic chlordiazepoxide (CDP), a benzodiazepine. In the present experiment, a range of doses (0-333.3 mg/kg) of CBD were administered in rats trained to discriminate 5.6 mg/kg CDP from saline. Due to the long time-course effects of CBD, generalization tests were conducted at 90 and 120 min post-CBD administration. Results indicate that CBD likely does not substitute for CDP, as mean percent CDP-appropriate responding remained under 20% at most doses. Future areas of investigation, including lowering the CDP training dose, could provide additional clarity regarding the present results.

Air pollution (AP) is a growing threat to human health including its effect on neurological development and function. AP is a complex mixture of gases and particulate matter, including trace elements, which may differentially contribute to its neurodevelopmental toxicity. In our lab, brains of neonate mice exposed to concentrated ambient ultrafine particulate matter showed brain accumulation of iron (Fe) and sulfur (S). To determine the neurodevelopmental impact of Fe and S specifically, male and female neonate mice were exposed to air or an aerosol mixture of ultrafine Fe and sulfur dioxide (n=12). Inhalation exposures occurred from postnatal day (PND) 4-7 and 10-13 for 4 hr/day. Following training on a fixed-interval schedule in adulthood, mice were trained on successive differential-reinforcement-of-low-rates schedules (10 - 36 s) followed by a discrimination reversal task. Peak deviation analysis of DRL responding showed relatively inaccurate timing in all groups across DRLs and no differences in within-bout response IRTs or overall reinforcers earned. Similarly, across three discrimination reversals, overall errors decreased, but there were no group differences in error patterns or response latencies. Thus, Fe and S in combination at the current dose may not recapitulate the behavioral impairments associated with developmental AP exposure.

Relative to nondrug reinforcers, illicit drugs may be more uncertain in terms of their availability, quality, and in the time and effort required to obtain them. In drug vs. nondrug choice, we have shown that a variable-ratio (VR) schedule of cocaine delivery increased cocaine’s potency as a reinforcer compared with an equal on average fixed-ratio (FR) schedule of cocaine delivery. However, it is unknown whether an history of chronic exposure to uncertain drug cost results in subsequent changes in the reinforcing properties of cocaine. Adult rhesus monkeys chose between cocaine (0-0.1 mg/kg/injection) and food (2 pellets/delivery) under concurrent FR FR schedules to establish baseline drug vs. nondrug choice functions. Subjects were then exposed to 60 days of cocaine availability (0.1 mg/kg/injection) under an FR 200 (fixed history) or VR 200 (uncertain history) schedule of reinforcement, followed by redetermination of cocaine vs. food choice functions. Then, subjects first exposed to the FR schedule experienced the VR schedule, and vice versa, followed by a final determination of cocaine vs. food choice. Thus far, cocaine choice is reduced or unchanged following a fixed history with cocaine and is increased following an uncertain history with cocaine. If replicated with additional subjects, these results suggest that exposure to uncertain drug costs could enhance the reinforcing properties of the drug compared with exposure to fixed drug costs.