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This thesis aims to examine the role of the hippocampus in declarative memory through the development of animal behavioural models of episodic memory for laboratory rats. Episodic memory- memory for unique events or episodes- is part of the declarative memory system thought to be mediated by the medial temporal lobe area of the brain in humans. One commonly used test of episodic memory in human subjects is paired associate learning. The first part of this thesis describes the adaptation of this human test for use with laboratory rats. Using their natural foraging tendency, rats were trained to search for different flavours of food at different locations within a large enclosure. When cued with a piece of food of a particular flavour in a separate box, rats learned to return to the place where that flavour of food had previously been found. This paradigm was used to investigate the role of the hippocampus in paired-associate learning using temporary pharmacological inactivation and permanent neurotoxic lesion techniques. The hippocampus has also been strongly implicated in spatial navigation, learning and memory in rats and humans. In the experiments described previously, attempts were therefore made to demonstrate that the results were not confounded by a simple deficit in spatial navigation. An alternative approach to studying episodic memory in the laboratory rat is to use the criteria established by Tulving in 1972 to describe episodic memory. He stated that episodic memory should encompass the memory for an event and the spatiotemporal context in which it occurred, i.e. the ”what”, ”where” and ”when” of an event. He later updated these criteria to include demonstration of autonoetic consciousness- most easily described as a sense of self awareness. Since this is difficult or impossible to demonstrate in animals, the term ”episodic-like” memory was coined (Clayton & Dickinson 1998) to describe the flexible use of information about the spatiotemporal aspects of an event by non-human species. Since it has been difficult to demonstrate the use of time (when) in rats (Bird et al; 2003, Babb & Crystal 2006a), Eacott & Norman (2004) suggested that the ”when” component could be replaced by context; i.e. another element specific to a particular event that they labelled ”which”. The next part of this thesis describes the use of the task published by Eacott & Norman to test episodic-like memory in the laboratory rat. Using the innate spontaneous behaviour of rats to explore novel aspects of their environment, they were exposed to multiple unique events. These consisted of various three-dimensional objects being presented in different locations within different contexts. Their memory for manipulations of the environment was then tested by presenting them with an event in which one combination of object, location and context was different from combinations which had previously been encountered. Due to their tendency to explore novel aspects of their environment, normal rats spent the majority of their time exploring the object that was in a novel location relative to the context in which it was presented. This successfully demonstrated integrated memory for what, where and which- similar to that previously defined by Tulving. The rats also showed that they could use this information flexibly because every trial involved unique combinations of objects, locations and contexts so there was no inadvertent semantic rule-learning involved. Permanent neurotoxic lesions of the hippocampus were used to determine the extent to which this structure is involved in memory for the what, where and which of an event. The experimental results presented in this thesis demonstrate an indisputable role for the hippocampus in a variety of tasks designed to parallel episodic memory in humans. The next steps in this line of research should involve characterisation of the roles of the various subregions of the hippocampus in episodic-like and paired associate memory.

Reperfusion of the isolated rat heart following 10 min of coronary artery ligation under constant flow conditions results in the development of arrhythmias - premature ventricular contractions (PVCs), ventricular tachycardia (VT) and ventricular fibrillation (VF). Increasing concentrations of magnesium (0 - 4.8 mM) and/or potassium (2.5 - 10.0 mM) attenuate, while calcium (0.6 - 2.4 mM) exacerbates these arrhythmias. The protective effects of magnesium and potassium were additive. Magnesium reduced heart rate, perfusion pressure and developed tension. Potassium reduced perfusion pressure and increased developed tension. These haemodynamic effects contributed to the antiarrhythmic action of magnesium but did not completely account for its antiarrhythmic action. Calcium increased developed tension and heart rate and reduced perfusion pressure. Post-ligation administration of magnesium and potassium also protected against reperfusion arrhythmias. These results demonstrate that reperfusion arrhythmias are significantly affected by the ionic environments of the heart. Superoxide dismutase (5 - 20 Um1-1 ), glutathione (10 -5 - 10-3M), ascorbic acid (10-4 -5 x 10-4 M) and histidine (5 x 10-3 M) when given before coronary artery ligation attenuated the development of reperfusion arrhythmias. Mannitol (2 x 10-2 M) and catalase (100 - 300 Uml-1) did not have any significant effect on reperfusion arrhythmias when given alone but they did potentiate the effect of superoxide dismutase. Glutathione and a combination of superoxide dismutase, catalase and mannitol also reduced the incidence of reperfusion induced ventricular fibrillation when given just before reperfusion. Ferrous ion exacerbated the severity of reperfusion arrhythmias. Mannitol (2 x 10-2 M), catalase (100 uml-1) and histidine (5 x 10-3 M) when given before coronary ligation or just before reperfusion prevented the effect of ferrous ion while superoxide dismutase did not, indicating that the presence of ferrous ion is important for the production of hydroxyl radicals. Pretreatment with 6- OHDA attenuated the incidence of reperfusion arrhythmias but pre-ligation administration of allopurinol had no effect on reperfusion arrhythmias. By perfusing hearts with ferricytochrome C it was possible to show an increased reduction of ferricytochrome C during the first minute of reperfusion which could be prevented by the addition of superoxide dismutase and 6-OHDA treatment. These results provide evidence that oxygen free radicals are produced and may be important in the genesis of reperfusion induced arrhythmias in the isolated rat heart. Adenosine (10-6 M), verapamil (10 -8 - 10-7 M), ZK 36374 (10-10 - 10 -9 M) and sodium nitroprusside (10-6 -10-9 M) attenuate the incidence of reperfusion arrhythmias which may be via a coronary steal effect. Agents which affect arachidonic acid metabolism yielded conflicting results which may reflect nonspecific mechanisms other than inhibition of arachidonic acid metabolism. Glutathione and a mixture of superoxide dismutase, catalase and mannitol when given before coronary ligation and just before reperfusion reduced the increase in 86 rubidium efflux rate constant shown on reperfusion. The effect of glutathione on 86 rubidium efflux may be at least in part due to its vasodilator effect. Superoxide generation by xanthine/xanthine oxidase system increased the rate of efflux of 86 rubidium. A mixture of superoxide dismutase, catalase and mannitol also reduced the transient increase in the rate of release of 3H-noradrenaline shown to be produced on reperfusion after 10 min of ischaemia in the isolated rat heart.

The aim of this project was to study changes in cardiovascular responses brought about by long term oral treatment of Wistar rats with beta adrenoceptor antagonists. After chronic treatment with propranolol (12 or 60 mg/kg/day for up to 6 weeks) or timolol (1.2, 2.5, 5 or 25 mg/kg/day for up to 17 weeks), the log dose-response curves for mean rises in heart rate and mean arterial pressure on stimulation of the postsynaptic adrenoceptors of the pithed rat by I.V. noradrenaline or isoprenaline were not significantly changed. Chronic propranolol treatment significantly reduced the response of the heart to electrical stimulation of the whole sympathetic outflow but treatment with timolol failed to alter the cardiac chronotropic response. The rises in mean arterial pressure on stimulation of the whole sympathetic outflow were not altered by long term treatment with either propranolol or timolol. The high dose of propranolol significantly reduced the heart rate of conscious rats. However neither the lower dose of propranolol nor any dose of timolol affected heart rate. The systolic pressure of conscious rats was unaltered by treatment with the beta adrenoceptor blockers. The threshold for release of tritiated noradrenaline from the sympathetic nerves on stimulation of the whole spinal outflow was raised by chronic treatment with propranolol or timolol. Timolol significantly increased the concentration of 3H noradrenaline in the blood and decreased the heart content of tritium. Chronic propranolol treatment did not alter the blood or heart levels of 3H noradrenaline. Thus, although the plasma levels of the beta adrenoceptor blocking drugs were probably insufficient to ensure prolonged blockade of postsynaptic receptors, significant changes in presynaptic function were observed. It remains to be seen whether these changes play any significant part in cardiovascular responses to beta adrenoceptor antagonists in clinical practice.

Various topics on functional magnetic resonance imaging (fMRI) analyses have been in study through the last 30 years. This work delineates the pathways required for resting-state functional connectivity analyses, which illuminates the correlations between different rat brain regions and can be presented in a functional connectivity matrix. The matrix is built based on the category nomenclature system of Swanson Rat Atlas 1998. From which a structural connectivity matrix is also built. This work developed the complete functional connectivity counterpart to the physical connections and explored the relationships between the functional and structural connectivity matrices. The functional connectivity matrices developed in this work map the entire rat brain. The results demonstrate that where structural connectivities exist, functional connectivities exist as well. The methodologies used to create the functional and structural analyses were completely independent.

The placenta provides a protective barrier for the developing foetus during gestation. Physiological barriers including the placenta, liver, kidney, intestine and blood-brain barrier are known to express ATP-Binding cassette transporters (ABC transporters) and metabolising enzymes. These specialised proteins have the ability to transport or metabolise xenobiotics. There is evidence to suggest that ABC transporters and metabolising enzymes are located at the interface between the maternal and foetal blood supplies (a cell layer referred to as the syncytiotrophoblast) and therefore may help protect the foetus from harmful xenobiotics. During new compound development prenatal developmental toxicity testing forms an important part of safety assessment. In order to predict potential toxicity of a new chemical entity to humans, rodent and non-rodent species are currently used. This thesis investigates the rat and human placental barrier properties in order to help facilitate our knowledge of species differences and contribute to our understanding of the limitations of these surrogate models. The approaches taken include: genomic analyses using microarray data to compare the overall expression of ABC transporters and metabolising enzymes throughout gestation in both species, immunohistochemical techniques to localise transporters and metabolising enzymes in the rat placenta, and in vitro functionality assays of selected transporters performed in rat and human placental cell line models. The main findings have shown a similar mRNA expression level of ABCG2/BCRP (breast cancer resistance protein) throughout gestation in the rat and human, however different mRNA expression levels of other transporters (slco4a1/oatp4a1 in particular) and metabolising enzymes were also highlighted. Immunohistochemistry localised selected transporters to the syncytiotrophoblast region of the rat placenta (the interface of maternal and foetal circulations). Functional in vitro assays were successfully utilised in rat and human placental cell lines which showed functional ABCB1/P-gp in both species. Overall, these findings provide a genomic characterisation of the rat and human protective placental barrier properties and show transporter functionality in in vitro cell-based assays which will prove useful in prenatal and developmental toxicity tests. Alternatives to using animals have been explored by using functional in vitro assays which could potentially be implored during the new compound discovery phase. This could help to make animal testing more selective for given compounds and ensures the new chemical entity is being tested in the model closest resembling the human.

Home ranges of dusky-footed wood rats (Neotoma fuscipes) were determined by the exclusive boundary strip method in two colonies 630 m apart in Klamath County, Oregon. The mean home range area was 1800 - 1900 m2 . Densities or trees and shrubs were determined on selected home ranges and densities of wood rat houses and nests were determined on all home ranges. No significant correlation was found between home range areas and densities of various trees and shrubs, home range areas and densities of woodrat houses and nests, or home range areas and weights of woodrats in those areas. No movement between colonies was observed.