Thesis (M.A)--University of North Carolina Wilmington, 2009. / Title from PDF title page (January 11, 2010) Includes bibliographical references (p. 122-135)

Thesis (M.A.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (January 12, 2010) Includes bibliographical references (p. 111-113)

Thesis (M.A.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (January 11, 2010) Includes bibliographical references (p. 63-68)

abstract: Nicotine is thought to underlie the reinforcing and dependence-producing effects of tobacco-containing products. Nicotine supports self-administration in rodents, although measures of its reinforcing effects are often confounded by procedures that are used to facilitate acquisition, such as food restriction, prior reinforcement training, or response-contingent co-delivery of a naturally reinforcing light. This study examined whether rats acquire nicotine self-administration in the absence of these facilitators. A new mathematical modeling procedure was used to define the criterion for acquisition and to determine dose-dependent differences in rate and asymptote levels of intake. Rats were trained across 20 daily 2-h sessions occurring 6 days/week in chambers equipped with active and inactive levers. Each active lever press resulted in nicotine reinforcement (0, 0.015, 0.03, 0.06 mg/kg, IV) and retraction of both levers for a 20-s time out, whereas inactive lever presses had no consequences. Acquisition was defined by the best fit of a logistic function (i.e., S-shaped) versus a constant function (i.e., flat line) for reinforcers obtained across sessions using a corrected Akaike information criterion (AICc) as a model selection tool. The results showed an inverted-U shaped function for dose in relation to the percentage of animals that acquired nicotine self-administration, with 46% acquiring at 0.015 mg/kg, 73% at 0.03 mg/kg, and 58% at 0.06 mg/kg. All saline rats failed to acquire as expected. For rats that acquired nicotine self-administration, multiple model comparisons demonstrated that the asymptote (highest number of reinforcers/session) and half learning point (h; session during which half the assymptote had been achieved) were justified as free parameters of the reinforcers/session function, indicating that these parameters vary with nicotine dose. Asymptote exhibited an inverted U-shaped function across doses and half learning point exhibited a negative relationship to dose (i.e., the higher the dose the fewer sessions to reach h). These findings suggest that some rats acquire nicotine self-administration without using procedures that confound measures of acquisition rate. Furthermore, the modeling approach provides a new way of defining acquisition of drug self-administration that takes advantage of using all data generated from individual subjects and is less arbitrary than some criteria that are currently used. / Dissertation/Thesis / M.A. Psychology 2011

This thesis focuses on individually specific differences in behavioural strategies, personalities, with two microtine rodents (Microtus arvalis and M. oeconomus) as study species. The work evaluates methodology necessary to reveal and measure consistent individual differences in behaviour, identifies possible proximate and ultimate mechanisms behind the existence of individual behavioural variability, and describes some ecological, evolutionary and behavioural consequences of personalities.

Estudos de placentação foram desenvolvidos em quatorze fêmeas de mocós em diferentes fases de gestação. As fêmeas foram pré-anestesiadas associando-se cloridrato de quetamina (15mg/kg) e midazolan (1mg/kg). Em seguida anestesiadas com isoflurano em associação com oxigênio com 100% de saturação. Após a anestesia realizou-se a cirurgia para a exposição das estruturas fetais e a coleta de dados. Macroscopicamente, identificou-se uma placenta discoidal, o saco vitelínico e o âmnio de aspecto transparente e avascular. Microscopicamente, o cordão umbilical apresentou duas artérias, uma veia e o ducto alantoideano, além de uma artéria e uma veia vitelínicas. A placenta mostrou uma relação mesometrial com o útero e apresentou-se constituída por lóbulos delimitados por regiões de interlóbulo e, perifericamente, uma região de sincício marginal contendo locais com espongiotrofoblasto e células trofoblásticas gigantes. A subplacenta esteve composta por lóbulos e por trofoblasto de natureza sincicial e celular. O saco vitelínico apresentou uma porção parietal sustentada pela membrana de Reichert´s e uma porção visceral muito vascularizada. Os estudos de placentação em mocós indicaram a presença de um útero bicórneo, uma placenta corioalantoídea discoidal e labiríntica, com barreira placentária hemocorial de subtipo hemomonocorial separando um fluxo sangüíneo materno-fetal do tipo contracorrente. / Placentation studies of fourteen rock cavy females in different gestation phases were conducted. Females were pre-anesthetized associating ketamine chloridrate (15mg/kg) and midazolan (1mg/kg). Soon afterwards, they were anesthetized by isoflurane inhalation in association with oxygen at 100% saturation. After anesthesia, the surgery allowed to exhibit fetal structures and then data collection was performed. Macroscopically, a discoidal placenta, vitelline sack and the amnion of a transparent aspect and avascular, were identified. Microscopically, the umbilical cord presented two arteries, a vein and the allantoid duct, besides an artery and a vitelline vein. The placenta showed a relationship between the mesometrium and the uterus and was constituted by lobes delimited by interlobular areas and, peripherically, by an area of marginal syncytium containing places with spongiotrophoblast and gigantic trophoblastic cells. The subplacenta was composed by lobules and by a trophoblast of syncytium and cellular nature. The vitelline sack showed a parietal portion sustained by the Reichert´s membrane and a well-vascularized visceral portion. The placentation studies in rock cavies indicated the presence of a bicornuate uterus, a chorioallantoid discoidal and labirynthic placenta, with a hemochorial placental barrier of hemomonochorial subtype separating the maternal-fetal countercurrent sanguine flow.

No description available.

Spermophilus lateralis, the golden-mantled ground squirrel, while euthermic exhibits a strong hypoxic ventilatory response, but a relatively blunted hypercapnic ventilatory response similar to other semi-fossorial mammals. Under resting conditions, carotid body chemoreceptors provide a tonic excitatory input to the frequency component of ventilation. Carotid body denervation (CBX) results in a 40% decrease in minute ventilation (V). The overall ventilatory response to hypoxia is unaffected by CBX, although the ventilatory threshold is significantly shifted to lower levels of inspired O₂. CBX also has little effect on the overall response to hypercapnia. Thus, in S. lateralis, it appears that changes in the partial pressure of O₂ (P0₂) In the blood act centrally, rather than peripherally, to play a predominate role in ventilatory control. Chronic exposure to hypoxia and hypercapnia (CHH, 17% O₂ and 4% CO₂) does not result in overall ventilatory acclimation, with minute ventilation being similar to control squirrels acutely exposed to hypoxic and hypercapnic conditions. In spite of this, CHH exposure does result in adjustments to respiration; frequency is decreased and tidal volume is elevated compared to control squirrels acutely exposed to CHH conditions. Overall V sensitivities to both hypoxia and hypercapnia are not significantly altered by CHH exposure. It appears that acclimation to chronic hypoxic and hypercapnic conditions in S. lateralis may increase alveolar minute ventilation relative to total minute ventilation and thus minimize the changes in arterial PO₂ and Pco₂ during hypoxic and hypercapnic exposure. During entrance into hibernation, as metabolic rate and body temperature decline, concomitant decreases in ventilation occur. Two patterns of respiration occur during deep hibernation; a burst breathing pattern characterized by long non-ventilatory periods (Tnvp) separated by bursts of several breaths and a single breath pattern characterized by single breaths separated by a relatively short Tnvp. In S. lateralis during hibernation at body temperatures between 6° and 10°C, a burst breathing pattern prevails. At slightly lower body temperatures, less than 4°C, a single breath breathing pattern prevails. Both burst breathing and single breath breathing squirrels have similar overall levels of resting minute ventilation. Burst breathing squirrels exhibit a significant respiratory response to hypoxia (3% O₂) and when the decreases in metabolic rate during hibernation are taken into account (air convection requirement) their hypoxic sensitivity is similar to that in awake S. lateralis. In contrast, single breath breathing squirrels do not respond to hypoxia at any level tested (down to 3% O₂). Both burst breathing and single breath breathing squirrels show large ventilatory repsonses to hypercapnia. In the burst breathing state hypercapnic sensitivity is significantly higher compared to the single breath breathing state, due to an augmented frequency response during burst breathing. In both groups of hibernating squirrels ventilation is increased during hypercapnia solely by decreases in the nonventilatory period. When ventilation is standardized for the decreases in metabolic rate during hibernation both burst breathing and single breath breathing S. laterlis exhibit a much higher hypercapnic sensitivity than that seen in awake S. lateralis. Carotid body denervation has little effect on ventilatory pattern generation or ventilatory sensitivities to hypoxia and hypercapnia in hibernating squirrels. It appears that during hibernation in S. lateralis, ventilation is controlled primarily by changes in the partial pressure of CO₂ (Pc0₂) in tne blood acting centrally to stimulate ventilation. The burst breathing pattern is produced centrally, as are the respiratory responses to hypoxia and hypercapnia. Thus, central mechanisms involved with ventilatory control are extremely important in both the euthermic state and the hibernating state, but the chemical stimuli regulating ventilation appear to be fundamentally different in euthermic and hibernating S. lateralis. / Science, Faculty of / Zoology, Department of / Graduate

Cranial and external measurements in 422 museum specimens of the common vole, Microtus arvalis, from Switzerland were examined to determine whether they varied with altitude in accordance with either (1) Bergmann's Rule, or (2) subspeciation. Correlation coefficients between altitude and size were calculated on 32 dimensions, each of which had been divided into sex segregated age groups. In not one of the 108 tests was correlation significant. The lack of adherence to Bergmann's Rule was investigated by (1) reviewing the basic concepts of the Rule, as applied to homeotherms; (2) identifying the major abiotic and biotic selection pressures that might affect growth in Microtus arvalis, including climate and competition with sympatric congenerics; and (3) indicating deficiencies in data derived from museum specimens which might have influenced the computations. There were several references in the literature to the occurrence of two subspecies of Microtus arvalis in Switzerland - the nominate subspecies M. a. arvalis (Pallas, 1779) and a montane subspecies called either M. a. incertus (Selys-Longchamps, 1841) or M. a. rufescentefuscus (Schinz, 1845). The lack of evidence in this study for the existence of two phenotypically and distributionally distinct subspecies was considered by (1) examining the general appropriateness of discussing variation in Microtus arvalis in terms of subspeciation; and (2) reviewing the literature on the diagnostic characters and distribution attributed to the montane morph. Two major conclusions were drawn. The first was that Bergmann's Rule should not be considered a "rule" until firm definitions are established on at least two of its founding precepts - the groups of animals to which it applies and the taxonomic level at which it applies - and until it is found to apply to a majority of the cases for which it is intended. The second conclusion was that for species like Microtus arvalis, in which growth is highly variable and distribution is by and large continuous, the usefulness of formal recognition of in-fraspecific populations is questionable until an overview of the geographic variability of the species as a whole is well documented. / Science, Faculty of / Zoology, Department of / Graduate

In North America, pikas (mammal genus Ochotona) are distributed throughout the western mountain ranges where they are mostly restricted to higher elevation talus slides. There are two species in North America, the Alaskan or Collared Pika (Ochotona collaris Nelson) and the American Pika (Ochotona princeps Richardson). The former is found north of 58 degrees north latitude and has no subspeciation, while the latter occurs south of 58 degrees latitude and consists of 35 subspecies isolated on various mountain ranges (Hall and Kelson 1959). In Utah there are nine subspecies, which are mostly distributed in the Wasatch range that runs northeast to southwest through Utah. They are also found in the LaSal Mountains and the Uinta Mountains, where this study was conducted. This subspecies of pika, Ochotona princeps uinta (Hollister) is found in the entire Uinta range and extends west into the central Wasatch Mountains.