Methamphetamine increases risky choice in rats, but only when magnitude and probability of reinforcement are manipulated within a session.

Risky choice is associated with maladaptive behaviors, particularly substance use disorders. Current animal models of risky choice are often confounded by other constructs like behavioral flexibility and suboptimal choice. The purpose of the current experiment was to determine if the psychostimulant methamphetamine, a drug whose popularity has increased in recent years, increases risky choice in an equivalent expected value (EEV) task. In the EEV task, rats are given a choice between two reinforcer alternatives that differ in magnitude and probability of delivery, but have equivalent expected value. Forty-eight Sprague Dawley rats were tested in three versions of the EEV task. In the first version of the EEV task, both reinforcer magnitude and probability were adjusted across blocks of trials for both alternatives. In the second and the third versions of the EEV task, reinforcer magnitude was held constant across each block of trials (either 1 vs. 2 pellets or 4 vs. 5 pellets). We found that male rats preferred the "riskier" option, except when reinforcer magnitudes were held constant at 4 and 5 pellets across each block of trials. Methamphetamine (0.5 mg/kg) increased preference for the risky option in both males and females, but only when both reinforcer magnitude and probability were manipulated across blocks of trials for each alternative. The current results demonstrate that both magnitude of reinforcement and probability of reinforcement interact to influence risky choice. Overall, this study provides additional support for using reinforcers with expected value to measure risky choice.

Rats have low motivation to self-administer oral methamphetamine across increasing response requirements.

Methamphetamine (METH) is a psychostimulant drug that has become increasingly popular in recent years, with overdose deaths more than doubling during the second half of the 2010s. As methamphetamine use disorder rates continue to increase, finding effective treatment strategies to decrease METH dependence is important. Animal studies are well-suited for studying the neurobiological mechanisms underlying addiction-like behaviors. Although individuals can ingest METH orally, few studies have examined oral METH self-administration in animals. Mice show decreased responding for oral METH as the response requirement increases across sessions. The purpose of the current study was to determine if rats show a similar decrease in motivation to earn oral METH across increasing response requirements. Sixteen Sprague Dawley rats were trained to emit a response in an aperture to receive a 0.1-ml METH solution (40 mg/l) according to an FR 1 schedule. The FR requirement increased across sessions to a terminal FR 10. Responses for METH decreased significantly when an FR 10 schedule was used. These results suggest that rats, similarly to mice, have low motivation to self-administer oral METH.

Effects of adolescent methylphenidate administration on methamphetamine conditioned place preference in an animal model of attention-deficit/hyperactivity disorder: Examination of potential sex differences.

BACKGROUND: Individuals with attention-deficit/hyperactivity disorder (ADHD) are more likely to be diagnosed with a substance use disorder; however, the effects of long-term psychostimulant treatment on addiction are mixed. Preclinical studies are useful for further elucidating the relationship between ADHD and addiction-like behaviors, but these studies have focused on male subjects only. The goal of the current study was to determine if early-life administration of methylphenidate (MPH) augments methamphetamine (METH) conditioned place preference (CPP) and/or potentiates reinstatement of CPP in both male and female rats. METHODS: Male and female spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats (WKYs) received either MPH (1.5mg/kg; p.o.) or vehicle (1.0ml/kg) during adolescence (postnatal day [PND] ~29-57). Two weeks after cessation of MPH treatment, rats were tested for METH CPP (1.0mg/kg or 2.0mg/kg; s.c.). Rats were then given extinction sessions. Once rats met extinction criteria, they were tested for reinstatement of CPP following a priming injection of METH (0.25mg/kg; s.c.). RESULTS: All groups developed METH CPP, except vehicle-treated SHR males and vehicle-treated WKY females conditioned with the higher dose of METH (2.0mg/kg). Female SHRs treated with MPH showed greater reinstatement of METH CPP compared to female SHRs treated with vehicle. Adolescent MPH treatment did not augment the locomotor-stimulant effects of METH in adulthood. CONCLUSIONS: These results demonstrate the importance of considering biological sex when prescribing psychostimulant medications for ADHD as long-term MPH administration may increase the risk of continued drug use in females with ADHD following a period of abstinence.

The behavioral effects of gestational and lactational benzo[a]pyrene exposure vary by sex and genotype in mice with differences at the Ahr and Cyp1a2 loci.

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) and known carcinogen in the Top 10 on the United States' list of priority pollutants. Humans are exposed through a variety of sources including tobacco smoke, grilled foods and fossil fuel combustion. Recent studies of children exposed to higher levels of PAHs during pregnancy and early life have identified numerous adverse effects on the brain and behavior that persist into school age and adolescence. Our studies were designed to look for genotype and sex differences in susceptibility to gestational and lactational exposure to BaP using a mouse model with allelic differences in the aryl hydrocarbon receptor and the xenobiotic metabolizing enzyme CYP1A2. Pregnant dams were exposed to 10 mg/kg/day of BaP in corn oil-soaked cereal or the corn oil vehicle alone from gestational day 10 until weaning at postnatal day 25. Neurobehavioral testing began at P60 using one male and one female per litter. We found main effects of sex, genotype and treatment as well as significant gene x treatment and sex x treatment interactions. BaP-treated female mice had shorter latencies to fall in the Rotarod test. BaP-treated high-affinity AhrbCyp1a2(-/-) mice had greater impairments in Morris water maze. Interestingly, poor-affinity AhrdCyp1a2(-/-) mice also had deficits in spatial learning and memory regardless of treatment. We believe our findings provide future directions in identifying human populations at highest risk of early life BaP exposure, because our model mimics known human variation in our genes of interest. Our studies also highlight the value of testing both males and females in all neurobehavioral studies.

Comparison of satellite reflectance algorithms for estimating turbidity and cyanobacterial concentrations in productive freshwaters using hyperspectral aircraft imagery and dense coincident surface observations.

We analyzed 37 satellite reflectance algorithms and 321 variants for five satellites for estimating turbidity in a freshwater inland lake in Ohio using coincident real hyperspectral aircraft imagery converted to relative reflectance and dense coincident surface observations. This study is part of an effort to develop simple proxies for turbidity and algal blooms and to evaluate their performance and portability between satellite imagers for regional operational turbidity and algal bloom monitoring. Turbidity algorithms were then applied to synthetic satellite images and compared to in situ measurements of turbidity, chlorophyll-a (Chl-a), total suspended solids (TSS) and phycocyanin as an indicator of cyanobacterial/blue green algal (BGA) abundance. Several turbidity algorithms worked well with real Compact Airborne Spectrographic Imager (CASI) and synthetic WorldView-2, Sentinel-2 and Sentinel-3/MERIS/OLCI imagery. A simple red band algorithm for MODIS imagery and a new fluorescence line height algorithm for Landsat-8 imagery had limited performance with regard to turbidity estimation. Blue-Green Algae/Phycocyanin (BGA/PC) and Chl-a algorithms were the most widely applicable algorithms for turbidity estimation because strong co-variance of turbidity, TSS, Chl-a, and BGA made them mutual proxies in this experiment.