The purpose of the present study is to examine swimming position, gait, stroke speed, speed over distance, endurance, and willingness to enter water in four species of mice found in the Sacramento-San Joaquin River Delta of California; Mus musculus, Reithrodontomys megalotis longicaudus, Miorotus californicus acstuarius, and Peromyscus maniculatus gambelii.

No description available.

Previous research has found that if a population were allowed to exceed a comfortable density level, then many catastrophic events occurred such as increased mortality among the young, cannibalism, homosexuality, and lack of maternal functions. The most influential researcher in this area is Calhoun (1962), after whose experimental design a pilot study was fashioned to replicate his results. The results of this pilot study inspired a more detailed research project of which this thesis is an account. Forty-eight albino mice of the Swiss Webster strain were divided into three groups of sixteen each. Each group consisted of ten females and six males chosen randomly; two groups were to serve as experimental groups and the other group as the control. The experimental groups were placed into apparatus 15 5/8” x 20 1/2"x 8" and the control group in an apparatus 47 7/8" x 61 1/2" x 8". The three groups were allowed to multiply freely with nesting material, food and water provided proportionately as their numbers grew. The experimental groups were allowed to overpopuate while the control group was not. There were six behavior variables noted as the experiment proceeded: (1) grooming, (2) homosexuality, (3) nest building, (4) retrieving of young, (5) fighting, and (6) mortality of the young. It was predicted that grooming, nest building, and retrieving of the young would decrease in frequency as the population increased, while fighting, homosexuality and mortality of the young would increase with the rising population density. The experiment was conducted for six months and fourteen days. The result of this experiment was a total lack of overpopulation. The two experimental groups never weaned any pups though they produced many, and the control group grew to the comfortable limits of its apparatus and then ceased weaning any further pups. In an effort to ascertain the reasons for these results, one of the experimental groups was artificially reduced in number; whereupon it promptly weaned forty-one percent of its first litter, thirty percent of its second, and none of its third. At the time of its first weaning, this group was technically overpopulated. In conclusion a hypothesis is proposed to explain the results. It is felt that each population has an innate knowledge of its comfortable limits with regard to density and will maintain this crucial density level if necessary. The group's ability to control its popu1ation is directly related to a time factor in that if a population were allowed to approach its crucial density level gradually it would not exceed it; however if there were little or no approach time, then this level would be exceeded.

GABA is the main inhibitory neurotransmitter of the central nervous system. GABA[subscript A]Rs are multimeric transmembrane receptors, which are composed of 5 subunits. It is known that there are 19 subunits that can make up the GABA[subscript A]Rs, allowing for a vast array of receptor subtypes. In addition to the GABA binding site GABA[subscript A]Rs have distinct allosteric binding sites for benzodiazepines, barbiturates, ethanol, certain general anaesthetics and neuroactive steroids. The molecular heterogeneity of the GABA[subscript A]R is accompanied by distinct pharmacological profiles of the different receptor subtypes. The advance of transgenic mouse models has allowed the functional significance of this heterogeneity to be studied in vivo. Therefore, this thesis utilises a variety of transgenic mouse models carrying either mutations or deletions of certain subunits to study the functional significance of the receptor heterogeneity. Mice lacking the α1 subunit (α1[superscript(-/-)]), carrying a point mutation of the α1 subunit (α1H101R), and mice lacking the δ subunit (δ[superscript(-/-)]) have been utilised to investigate the role of these subunits in the sedative actions of benzodiazepines and the GABA[subscript A]R agonist THIP. Although there are limitations to the interpretation of these results due genetic background of the α1[superscript(-/-)] and α1H101R, experiments suggest that the α1H101R mutation is not behaviourally silent as previously suggested and provide further evidence that the α1 subunit mediates the sedative properties of benzodiazepines. These experiments also reveal that the extrasynaptic δ containing receptors are responsible for mediating the sedative effects of THIP, and these findings combined with evidence from collaborators, implicates the thalamus as an anatomical mediator of these effects. An investigation of the putative cognitive enhancing effects of THIP using an attentional set-shifting task for mice suggested that pre-treatment with THIP reduces the number of errors to reach criterion. δ[superscript(-/-)] mice could not be trained to perform the task, therefore further behavioural investigation of these mice was performed, which suggested a heightened level of anxiety and reduced motivation for a food reward. This thesis has furthered our understanding of the functional role of GABA[subscript A]R subtypes. With the advance in genetic manipulations that allow for regionally selective mutations of the receptor the anatomical structures involved in these functions can be identified.

Thesis (M.A.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 34-45). / 52 leaves, bound ill. 29 cm

Indiana University-Purdue University Indianapolis (IUPUI) / Sensitization to the locomotor stimulant effects of alcohol (ethanol) is thought to be a heritable risk factor for the development of alcoholism that reflects progressive increases in the positive motivational effects of this substance. However, very little is known about the genetic influences involved in this phenomenon or the extent to which ethanol’s positive motivational effects are altered in parallel to its development. The first goal of this work was to determine the heritability of ethanol-induced locomotor sensitization in mice using short-term behavioral selection. Genetically heterogeneous C57BL/6J (B6) x DBA/2J (D2) F2 mice were generated from B6D2F1 progenitors, phenotyped for the expression of locomotor sensitization, and bred for high (HLS) and low (LLS) expression of this behavior. A secondary goal was to characterize possible line differences in ethanol’s positive motivational effects using a conditioned place preference assay. There were large and significant differences in locomotor sensitization between HLS and LLS lines by the fourth generation. Twenty-two percent of the observed line difference(s) were attributable to genes (h2=.22). However, there were no significant differences in conditioned place preference between lines despite significant line differences in ethanol-stimulated locomotion following repeated exposures. The results of this work have several implications. First, that changes in ethanol sensitivity following repeated exposures are in part genetically regulated highlights the relevance of studies aimed at determining how genes regulate susceptibility to ethanol-induced behavioral and neural adaptations. Additionally, the lack of line differences in ethanol-induced CPP, and the observation that CPP and ethanol sensitization are dissociable, suggests that 1) different genes regulate these two behaviors and 2) the utility of locomotor sensitization as a model of alterations in ethanol’s positive motivational effects is, at best, still unclear. Together these studies provide evidence that genes are capable of regulating alterations in ethanol-induced locomotor behavior but provide little support for ethanol-induced locomotor sensitization as a model for increases in ethanol’s positive subjective effects in mice.

Indiana University-Purdue University Indianapolis (IUPUI) / The present study sought to identify the effects of chronic lithium administration on ethanol intakes in high alcohol-preferring (HAP) mice. Lithium is a well-established treatment for bipolar disorder and has demonstrated efficacy in reducing impulsivity, an endophenotype of the disease. Impulsivity is also a prominent trait of alcoholism. HAP mice display a preference for consuming substantial amounts of ethanol and exhibit abnormally high levels of impulsivity. Previous work has determined that chronic lithium exposure in HAP mice reduces their levels of impulsivity. The present study analyzed fluctuations in established intake patterns after lithium exposure and how pre-exposure to lithium would affect ethanol intake acquisition. The results showed an increase in ethanol intake and no change in preference for ethanol over water in lithium treated mice. There was an increase in overall total fluid consumption in these mice, likely resulting from polydipsic effects. There also appeared to be a potentiated lithium toxicity effect found in those mice pre-exposed to lithium. The conclusion was that lithium therapy does not decrease ethanol consumption in HAP mice.

Indiana University-Purdue University Indianapolis (IUPUI) / Alcohol related problems and abuse continue to be serious problems in the U.S. today affecting nearly 17.6 million Americans. Understanding of the specific genes and related behaviors associated with alcohol use may provide substantial preventative measures for those who are at an increased risk. Genetically selected lines such as the high-alcohol preferring (HAP) and low-alcohol preferring (LAP) mice have been created to examine which endophenotypes co-segregate with alcohol preference. One behavioral trait that has been commonly associated with alcohol related problems is impulsivity. Impulsivity is the inability to withhold a response (motor impulsivity) or to act without forethought (cognitive impulsivity). The latter comprises much of the research and literature today using delay discounting models to tease out differences in subject’s wiliness to discount larger reinforcers for smaller immediate reinforcers. This study utilized relatively two newer paradigms associated with motor impulsivity in attempt to test differences in response disinhibition between two independent replicate HAP and LAP lines. It is hypothesized that the genes responsible for alcohol preference would be genetically correlated with motor impulsivity as HAP mice would display a greater degree of response disinhibition. Two independent replicates consisting of 48 mice (24 HAP II and 24 LAP II, representing the 37th generation; 24 HAP III and 24 LAP III, representing the 13th generation) were tested in two separate identical experiments. Each experiment was comprised of three phases. Phase I utilized a fixed interval (FI) 120s procedure for 30 days. After the 30 days of FI exposure mice were immediately moved to phase II for 10 days which implored a differential reinforcement of low rate procedure (DRL) at a time interval of 20s. Phase III used the same procedures as Phase II except the DRL was increased to 32s. As hypothesized, there was a moderate genetic correlation between alcohol preference and impulsivity as the HAP II mice displayed greater response disinhibition throughout all three phases compared to the LAP II mice. No differences were observed amongst the replicate III mice in any of the three phases. The findings from this study provide additional support that a genetic correlation between alcohol preference and impulsivity exists as seen in the delay discounting literature. Though this was observed in only one of the two replicates, interpretations must be taken at caution as the replicate III mice are still in the early stages of selection. It is possible at this stage in the selection process that increases in alcohol over successive generations are associated with selecting for taste until a threshold is met where selection shifts to pharmacologic drinking relevance. Until later generations of replicate III mice are studied where pharmacologic drinking occurs, conclusions from this study provide a moderate genetic correlation between alcohol preference and impulsivity.

Indiana University-Purdue University Indianapolis (IUPUI) / Abuse of alcohol during adolescence continues to be a problem, and it has been shown that earlier onset of drinking predicts increased alcohol abuse problems later in life. High levels of impulsivity have been demonstrated to be characteristic of alcoholics, and impulsivity has also been shown to predict later alcohol use in teenage subjects, showing that impulsivity may be an inherent underlying biological process that precedes the development of alcohol use disorders. These experiments examined adolescent drinking in a high-drinking, relatively impulsive mouse population, and assessed its effects on adult drinking and adult impulsivity. Experiment 1: Selectively bred High-Alcohol Preferring (HAP II) mice, which are shown to be highly impulsive, were given either alcohol (free choice access) or water only for two weeks during middle adolescence or adulthood. All mice were given free choice access to alcohol following 30 days without access, in adulthood. Experiment 2: Adolescent HAP II mice drank alcohol and water, or water alone, for two weeks, and were then trained to perform a delay discounting task as adults to measure impulsivity. In each experiment, effects of volitional ethanol consumption on later behavior were assessed. We expected adolescent alcohol exposure to increase subsequent drinking and impulsivity. Adolescent mice consumed significant quantities of ethanol, reaching average blood ethanol concentrations (BECs) of 142 mg/dl in Experiment 1 and 108 mg/dl in Experiment 2. Adult mice reached average BECs of 154 mg/dl in Experiment 2. Mice pre-exposed to alcohol in either adolescence or adulthood showed a transient increase in ethanol consumption, but we observed no differences in impulsivity in adult mice as a function of whether mice drank alcohol during adolescence. These findings indicate that HAP II mice drink intoxicating levels of alcohol during both adolescence and adulthood, and that this volitional intake has long-term effects on subsequent drinking behavior. Nonetheless, this profound exposure to alcohol during adolescence does not increase impulsivity in adulthood, indicating that long-term changes in drinking are mediated by mechanisms other than impulsivity. Importantly, this research demonstrates that the HAP II mouse is a good candidate for a model of heavy adolescent alcohol consumption.