Behavioral Evaluation of Seeking and Preference of Alcohol in Mice Subjected to Stress

The alcohol preference model is one of the most widely used animal models relevant to alcoholism. Stressors increase alcohol consumption. Here we present a protocol for a rapid and useful tool to test alcohol preference and stress-induced alcohol consumption in mice. In this model, animals are given two bottles, one with a diluted solution of ethanol in water, and the other with tap water. Consumption from each bottle is monitored over a 24-h period over several days to assess the animal's relative preference for the ethanol solution over water. In the second phase, animals are stressed by restraining them for an hour daily and their subsequent preference of tap water or the ethanol solution is evaluated. Preference is measured by the volume and/or weight or liquid consumed daily, which is then converted to a preference ratio. The alcohol preference model was combined with the conditioned place preference paradigm to determine alcohol conditioning and preference following the deletion of CB2 cannabinoid receptors in dopaminergic neurons in the DAT-Cnr2 Cre-recombinant conditional knockout (cKO) mice in comparison with the wild-type control mice.

Cannabinoid type 2 receptors in dopamine neurons inhibits psychomotor behaviors, alters anxiety, depression and alcohol preference

Cannabinoid CB2 receptors (CB2Rs) are expressed in mouse brain dopamine (DA) neurons and are involved in several DA-related disorders. However, the cell type-specific mechanisms are unclear since the CB2R gene knockout mice are constitutive gene knockout. Therefore, we generated Cnr2-floxed mice that were crossed with DAT-Cre mice, in which Cre- recombinase expression is under dopamine transporter gene (DAT) promoter control to ablate Cnr2 gene in midbrain DA neurons of DAT-Cnr2 conditional knockout (cKO) mice. Using a novel sensitive RNAscope in situ hybridization, we detected CB2R mRNA expression in VTA DA neurons in wildtype and DAT-Cnr2 cKO heterozygous but not in the homozygous DAT-Cnr2 cKO mice. Here we report that the deletion of CB2Rs in dopamine neurons enhances motor activities, modulates anxiety and depression-like behaviors and reduces the rewarding properties of alcohol. Our data reveals that CB2Rs are involved in the tetrad assay induced by cannabinoids which had been associated with CB1R agonism. GWAS studies indicates that the CNR2 gene is associated with Parkinson's disease and substance use disorders. These results suggest that CB2Rs in dopaminergic neurons may play important roles in the modulation of psychomotor behaviors, anxiety, depression, and pain sensation and in the rewarding effects of alcohol and cocaine.

Dietary docosahexaenoic acid alleviates autistic-like behaviors resulting from maternal immune activation in mice

The prevalence of autism spectrum disorders over the last several decades has risen at an alarming rate. Factors such as broadened clinical definitions and increased parental age only partially account for this precipitous increase, suggesting that recent changes in environmental factors may also be responsible. One such factor could be the dramatic decrease in consumption of anti-inflammatory dietary omega-3 (n-3) polyunsaturated fatty acids (PUFAs) relative to the amount of pro-inflammatory omega-6 (n-6) PUFAs and saturated fats in the Western diet. Docosahexaenoic acid (DHA) is the principle n-3 PUFA found in neural tissue and is important for optimal brain development, especially during late gestation when DHA rapidly and preferentially accumulates in the brain. In this study, we tested whether supplementation of a low n-3 PUFA diet with DHA throughout development could improve measures related to autism in a mouse model of maternal immune activation. We found that dietary DHA protected offspring from the deleterious effects of gestational exposure to the viral mimetic polyriboinosinic-polyribocytidilic acid on behavioral measures of autism and subsequent adulthood immune system reactivity. These data suggest that elevated dietary levels of DHA, especially during pregnancy and nursing, may help protect normal neurodevelopment from the potentially adverse consequences of environmental insults like maternal infection.

Psychiatric disturbances regulate the innate immune system in CSF of conscious mice

Environment may affect brain activity through cerebrospinal fluid (CSF) only if there are regulatory molecules or cascades in CSF that are sensitive to external stimuli. This study was designed to identify regulatory activity present in CSF, better elucidating environmental regulation of brain function. By using cannulation-based sequential CSF sampling coupled with mass spectrometry-based identification and quantification of proteins, we show that the naive mouse CSF harbors, among 22 other pathways, the innate immune system as a main pathway, which was downregulated and upregulated, respectively, by acute stressor (AS) and acute cocaine (AC) administrations. Among novel processes and molecular functions, AS also regulated schizophrenia-associated proteins. Furthermore, AC upregulated exosome-related proteins with a false discovery rate of 1.0 × 10(-)(16). These results suggest that psychiatric disturbances regulate the neuroimmune system and brain disorder-related proteins, presenting a sensitive approach to investigating extracellular mechanisms in conscious and various mouse models of psychiatric disorders.

Consequences of cannabinoid and monoaminergic system disruption in a mouse model of autism spectrum disorders

Autism spectrum disorders (ASDs) are heterogenous neurodevelopmental disorders characterized by impairment in social, communication skills and stereotype behaviors. While autism may be uniquely human, there are behavioral characteristics in ASDs that can be mimicked using animal models. We used the BTBR T+tf/J mice that have been shown to exhibit autism-like behavioral phenotypes to 1). Evaluate cannabinoid-induced behavioral changes using forced swim test (FST) and spontaneous wheel running (SWR) activity and 2). Determine the behavioral and neurochemical changes after the administration of MDMA (20 mg/kg), methamphetamine (10 mg/kg) or MPTP (20 mg/kg). We found that the BTBR mice exhibited an enhanced basal spontaneous locomotor behavior in the SWR test and a reduced depressogenic profile. These responses appeared to be enhanced by the prototypic cannabinoid, Δ(9)-THC. MDMA and MPTP at the doses used did not modify SWR behavior in the BTBR mice whereas MPTP reduced SWR activity in the control CB57BL/6J mice. In the hippocampus, striatum and frontal cortex, the levels of DA and 5-HT and their metabolites were differentially altered in the BTBR and C57BL/6J mice. Our data provides a basis for further studies in evaluating the role of the cannabinoid and monoaminergic systems in the etiology of ASDs.

A nonsynonymous polymorphism in cannabinoid CB2 receptor gene is associated with eating disorders in humans and food intake is modified in mice by its ligands

Marijuana use activates cannabinoid receptors (CB-Rs) producing several behavioral effects related to addiction, mood, and appetite. We investigated the association between CNR2 gene, which encodes cannabinoid CB2 receptor (CB2-R) and eating disorders in 204 subjects with eating disorders and 1876 healthy volunteers in Japanese population. The effect of treatment with CB2-R ligands on mouse food consumption was also determined. The CB2-R ligands used suppressed food intake in a time- and strain-dependent manner when food was available ad libitum and during the 12-h fast except, AM 630-the CB2-R antagonist that stimulated food consumption in food-deprived mice. There is an association between the R63Q polymorphism of the CNR2 gene and eating disorders (P = 0.04; Odds ratio 1.24, 95% CI, (1.01-1.53). These results suggest that cannabinoid CB2-R is involved in the endocannabinoid signaling mechanisms associated with the regulation of food intake and in eating disorders.

Behavioral effects of CB2 cannabinoid receptor activation and its influence on food and alcohol consumption

Consumers of marijuana typically feel a strong, compulsive desire to consume food. Although past research revealed that the CB1 cannabinoid receptor is a potent regulator of food intake, the functional presence of neuronal CB2 cannabinoid receptors in the brain has been controversial. The role of CB2 receptors in food and alcohol consumption and the behavioral effects of CB2 receptor ligands are not well characterized. This is because CB2 cannabinoid receptors were thought to be absent from the brain and expressed primarily in immune cells and in the periphery. We tested the effects of peripheral injections of CB2 antagonist AM 630, CB2 agonist PEA, and CB1 antagonist AM 251 on male C57BL/6, Balb/c, and DBA/2 mice at the beginning of the night cycle and after overnight 12-hour fasts. We also investigated the effects of the putative CB2 agonist, JWH015, and CB2 antagonist, SR144528, in mouse motor function tests and in the two-compartment black and white box. Under standard conditions, the CB2 antagonist AM 630 inhibited food consumption in C57BL/6 mice and DBA/2 mice, but failed to block food intake of Balb/c mice. The CB2 agonist PEA had no significant effect on food consumption in Balb/c mice, and reduced food intake in C57BL/6 and DBA mice. The CB1 antagonist AM 251 inhibited food ingestion in the three mouse strains at variable times. After 12-hour food deprivation, the CB2 antagonist AM 630 increased food consumption in C57Bl/6 mice, but failed to produce significant changes in food intake for Balb/c and DBA/2 mice. The CB2 agonist PEA also reduced food consumption in all three mice strains at variable times. In comparison to the CB2 ligands, CB1 antagonist AM 251 inhibited food ingestion in the mouse strains. A general pattern of depression in locomotor activity was induced by JWH 015 in both males and females in the three mouse strains tested as the dose was increased. The development and enhancement of alcohol preference was observed after chronic treatment with CB2 agonist JWH 015 in stressed mice, but not in controls. In the DBA/2 strain, the spontaneous locomotor activity and stereotype behavior was enhanced by acute administration of low doses of SR144528. There was a reduction in CNR2 gene expression in the ventral mid-brain region of mice that developed alcohol preference, but not in those that did not develop alcohol preference. These effects of CB2 cannabinoid receptor ligands in in vivo behavioral tests are provided as functional evidence that CB2-Rs in the brain play a role in food and alcohol consumption and in the modification of mouse behavior.

Genetic and developmental influences on infant mouse ultrasonic calling. III. Patterns of inheritance in the calls of mice 3-9 days of age

Infant mice produce ultrasonic calls that may elicit retrieval by adult mice. Age-related differences and genetic effects, such as additivity and directional dominance, have been found for most call characteristics at 3 days of age. Significant maternal effects have been reported for calling rate. However, little is known about how the influence of these genetic effects changes with age. This study explored developmental-genetic patterns of inheritance of seven ultrasonic call characteristics at ages 3-9 days, from groups of mice derived from a complete 4 x 4 diallel cross. The results indicate that additive variance contributes significantly to all characteristics for all ages. Maternal effects have a small effect on call characteristics. Dominance effects decrease with age for rate, range, and length of calls, suggesting less selective pressure toward higher rates, greater range, and longer calls as pups become more competent thermoregulators.

Prenatal cocaine exposure alters maternal retrieval behavior in mice

Previous studies have demonstrated alterations in maternal retrieval behavior as a result of direct cocaine exposure. To establish the influence of prenatal cocaine exposure on pup retrieval, we exposed pups of three F1 genotypes by injecting their mothers (all C57BL/10J strain) with 20 mg/kg cocaine hydrochloride or saline subcutaneously on gestation days 7 to 17. When those pups became adults, control and exposed females were mated with males of the same genotype and tested for pup retrieval on postpartum days 4 and 5. Because ultrasonic calls are known to be elicitors of maternal retrieval behavior, the rate of ultrasonic calling was measured. Prenatal cocaine exposure exerted a significant effect upon retrieval latency on day 4. No relationship was found between genotype and retrieval latency.

The effects of cold, rotation, and genotype on the production of ultrasonic calls in infant mice

There has been a revival of interest recently in the ultrasonic calls of infant rodents as investigators are using them to assess neurobehavioral development and animal models of anxiety. We compared the rates of ultrasonic calling of infant mice of two genotypes in two situations, cold and rotation. The subjects of study were 169 mouse pups from 29 litters and of two F1 genotypes, C57BL/10J x DBA/2J and C57BL/10J x SJL/J. Half of each litter was recorded in a cool situation for 20 seconds and the other half was recorded while rotating at 10 rpm for 20 seconds. All pups were recorded on days of age 2 to 8. Rotation elicited calling at about twice the rate as cool temperature on each day of age and on average across days; situation (cold or rotation) accounted for over 50% of the variation between litters. Genotype also altered call rate, and on some days situation and genotype interacted. In studies of neurobehavioral development and the effects of pharmacological agents on infant mice, it is particularly important to understand the roles of the stimuli and genotypes employed.

Nitric oxide in CsA-induced hypertension: role of beta-adrenoceptor antagonist and thromboxane A2

Cyclosporine A (CsA) is an immunosuppressive agent, which also causes hypertension. The effect of CsA on vascular responses was determined in Sprague-Dawley rats and rat aortic rings. Male rats weighing 250-300 g were given either CsA (25 mg/kg/day) in olive oil or vehicle by intraperitoneal (ip) injection for 7 days. CsA administration produced a 42% increase (P < 0.001) in mean arterial pressure (MAP) which reached a plateau after 3 days. The level of both nitrate/nitrite (NO2/NO3), metabolites of nitric oxide (NO), decreased by 50% (P < 0.001), but the level of thromboxane A2 (TBXA2) increased by 75% (P < 0.001), in the urine. When 10(-9) M of CsAwas added acutely to intact aortic rings from untreated rats, NO2/NO3 production decreased by 83% (P < 0.011), but TBXA2 production increased by 86% (P < 0.001). The effects of CsA were reversed both in vivo and in vitro by pretreatment with propranolol (15 mg/kg/day ip), beta-adrenoceptor antagonist. There were no changes in MAP and tension in rats treated with prop alone. In addition, in aorta of rats that were treated with CsA ip for 7 days, CsA significantly activated protein kinase C (PKC) translocation. This suggests that PKC mediate, in part, CsA-induced hypertension. In summary, CsA inhibits endothelial NO formation, activate PKC, and increaseTBXA2 production, with resulting increase in MAP, and this changes can be overcome by pretreatment with propranolol.

The effects of prenatal cocaine exposure and genotype on the ultrasonic calls of infant mice

Estimates are that as many as 44,000 humans are exposed to cocaine in utero per year. In this study we examined the effects of prenatal cocaine exposure on one aspect of the mother-infant relationship in mice, infant ultrasonic calls. We mated C57BL/10J female mice with males of three different inbred strains (producing pups of three different F(1) genotypes). We injected those females, subcutaneously, with saline or 20 mg/kg of cocaine hydrochloride on days 7-17 of gestation. That dosage did not compromise mother or pup viability, weight, or gestation length. On postnatal days 2-4, we recorded and measured the calls of pups while they were separated from their nest and slightly chilled. The results indicate changes in the ultrasonic calls as a function of cocaine and genotype. Overall, cocaine reduced the number of calls and increased the beginning pitch of calls. Pups of one genotype, a C57BL/10JxSJL/J hybrid were unaffected by cocaine exposure. The effects of cocaine, though reliable, were small, explaining only 1-2% of the total sum of squares. The size of the effect is in part due to the differential effect of cocaine on different genotypes.

Genetic and developmental influences on infant mouse ultrasonic calling. II. Developmental patterns in the calls of mice 2-12 days of age

Infant house mice, Mus musculus, produce ultrasonic calls that reliably lead to retrieval by adult mice. While individual differences in calls have been demonstrated both among and within species, the influences of age and sex on call characteristics have not been systematically investigated in mice. This study examined the influences of age, sex, and genotype (inbred versus hybrid) on the rate, length, and frequency characteristics of the calls of 486 male and female mice from 2 to 12 days of age. Rate of calling followed a shallow inverted U-shaped function across days. Call lengths decreased and call frequency characteristics increased, in a linear manner, with age. Females emitted fewer calls, with a smaller bandwidth, at some ages than males. Hybrid pups produced more calls of greater length and a lower frequency than inbred pups. These results indicate the presence of cues that could allow adult mice to behave differentially toward pups as a function of their age and sex.

Genetic and developmental influences on infant mouse ultrasonic calling. I. A diallel analysis of the calls of 3-day olds

Ultrasonic calls produced by young mice reliably elicit investigation and retrieval by adults. While there are large individual differences in the characteristics of these calls, little work has been done to partition that variation. We completed a 4 x 4 diallel cross and Hayman analyses on several characteristics of these cries. The major result was the detection of directional dominance toward a higher rate of calling, longer calls, and calls of lower overall frequency with a greater bandwidth. Within the context of biometrical genetic theory, we conclude that calls with such characteristics may have important fitness value. Extending this idea, we propose that within the population sampled for this study (the animals of the four inbred strains and 12 F1 hybrid groups), the calls most effectively eliciting investigation and retrieval would be calls with the average hybrid values of the diallel cross.

Issues in the genetics of social behavior: revisited

Though social behavior has not been overlooked by behavior geneticists, the number of studies is small when compared to those on individual traits. One reason for the neglect may be the difficulty of making connections between genes and social behaviors, which by definition involve the interaction of two or more organisms. Fuller and Hahn (1976) addressed this issue and described three means of establishing social groups that would facilitate genetic analysis. We survey the literature on agonistic behavior in mice from 1976 through 1994 and describe interesting uses of those three methods. One of those methods (the standard tester design) often employs a "noninteractive" social partner. We present data showing that the standard tester design may be more valuable when using an evocative and interactive standard tester.