The hippocampus and non-hippocampal long-term memory systems each have the capacity to learn and express contextual fear memory. How these systems interact during learning and remembering revolves around hippocampal mediated interference, where the hippocampus dominates for both the acquisition and expression of long-term memory. Hippocampal interference during learning can be overcome by modifying learning parameters such that learning is distributed across multiple independent sessions. The standard view of the role of the hippocampus in long-term memory retrieval is that it is temporally limited, where recently acquired memory is dependent on hippocampal function though as a memory ages, dependency is transferred to other memory systems by a process called systems consolidation. Distributed training demonstrates that learning parameters create a memory that is resistant to hippocampal damage. We find little evidence to support temporally based systems consolidation, and present data that supports the view that if the hippocampus is initially involved in learning a memory, it will always be necessary for accurate retrieval of that memory. A critical assessment of the rat literature revealed that initial memory strength, and/or lesion techniques might be responsible for the few studies that report temporally graded retrograde amnesia using contextual fear conditioning. Our experiments designed to directly test these possibilities resulted in flat gradients, providing further evidence that the hippocampus plays a permanent role in long-term memory retrieval. We propose and assess alternatives to the standard model and conclude that a dual store model is most parsimonious within the presented experiments and related literature. Interactions of the hippocampus and non-hippocampal systems take place at the time of learning and remembering, and are persistent over time. / xvi, 161 leaves : ill. (some col.) ; 29 cm

This thesis examines both behavioral and anatomical effects of prenatal exposure of Valproic Acid (VPA) on Long Evans rats. Tactile stimulation (TS) is then used to investigate its’ effect on remediating any abnormalities VPA may produce. Several behavioral tests were done to assess the behavioral effects of VPA and TS. It was found that VPA had an effect of many of the tasks, whereas, TS had almost none with the exception of an effect on females in the elevated plus maze. However, anatomical data showed that TS had a profound effect on neuronal branch order, cell complexity, and spine density in pyramidal neurons in the medial prefrontal cortex, the orbitofrontal cortex and the amygdala. Where VPA decreased the above in all of these areas, TS increased neuronal complexity in the aforementioned structures. This study demonstrates that prenatal exposure to VPA is a viable model of autism in rats and that TS has significant anatomical effects in these animals as well as in control animals / xi, 98 leaves; 29 cm

NMDA receptor antagonists such as Ketamine and PCP are potent psychoactive drugs used recreationally. This class of drug induces a number of phenomena in humans similar to those associated with schizophrenia including reduced selective attention, altered working memory, thought disorders and hallucinations. These psychotomimetic drugs have thus been used as a longstanding model to study this disease in animals. Importantly, such animal models allow for recording of brain activity using invasive techniques that are inappropriate in humans. Previous electrophysiological studies have shown that MK-801, a potent non-competitive NMDA receptor antagonist, increases gamma-frequency oscillations and produces a state of disinhibition in the prefrontal cortex of rats wherein the activity of putative excitatory pyramidal neurons increases while the activity of putative inhibitory interneurons decreases. These features are relevant to schizophrenia because molecular evidence suggests dysfunction of inhibitory cortical interneurons, while electroencephalographic recordings show altered gamma-frequency oscillations in this disease. It has been hypothesized that the disinhibited cortical state produces “noisy” information processing, but this has not been directly observed in the interaction of neuronal firing in either humans or animal models. We therefore tested this hypothesis by examining the synchronization of neural activity in the NMDA receptor antagonist model of schizophrenia. We used high-density electrophysiological recordings in the medial prefrontal cortex of freely moving rats before and after systemic injection of MK-801. Analysis of these recordings revealed that drug administration: (i) increases gamma power in field potentials in a manner dissociated from increased locomotion; (ii) does not change the gamma power in multi-unit activity; (iii) decreases spike synchronization among putative pyramidal neurons in the gamma range (30ms), and despite of this it (iv) does not change the synchronization between gamma-range field potentials or between sum-of-spikes and field potentials. These effects in synchronization may be revealing of potent cognitive effects associated with NMDA receptor antagonism, and may reflect impaired communication processing hypothesized to occur in schizophrenia. / xi, 42 leaves : ill. ; 29 cm

No description available.

The structural and functional integrity of a developing and maturing fetal and neonatal lung is critically dependent on carbohydrate metabolism. The energy derived from carbohydrate metabolism is utilized during the processed of cell growth and development. It is reported that maternal nicotine exposure during pregnancy and lactation results in the irreversible inhibition of glycolysis, for which no mechanism is currently proposed and a significant increase in glucose turnover. The principal objective of this thesis was to determine the influence of maternal nicotine exposure during gestation and lactation on the isoenzyme patterns and transcript levels of the selected enzymes in developing neonatal rat lung, in an attempt to elucidate the mechanism of inhibition of glycolysis observed.

This thesis discussed the cardiovascular effects of the aqueous leaf extract and a fraction of the methanol extract of Leonotis leonurus, a plant commonly used in traditional medicine in South Africa for the treatment of hypertension and other cardiac problems. The cardiovascular effects was tested on anaesthetized normotensive male Wistar rats and isolated perfused rat hearts.

<p>Crinum macowanii (C. macowanii) (Amaryllidacea) as authenticated by Mr. F. Weitz at the Herbarium, University of the Western cape, is widely used a traditional remedy and is thought to have therapeutic value (Fennell and van Staden 2001). The objective of this study was to determine the cardiovascular effects of the crude aqueous extract of Crinum macowanii on the rat and to determine the effect of pre-treatment drugs on Crinum macowanii in in vivo, anaesthetized normotensive, male Wistar rats (200-250 g.).</p>

Bibliography: leaves 249-283. / xi, 283 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis examines the hypothesis that cerebrospinal fluid (CSF) is driven from the subarachnoid space into perivascular spaces and the central canal by arterial pulsations and that this is the driving force for the development of non-communicating syringomyelia. Horseradish peroxidase (HRP) is used as a CSF tracer in rats and sheep. A technique for studying the three-dimensional morphology of the human central canal is also developed. / Thesis (Ph.D.)--University of Adelaide, Dept. of Surgery, 1997?

Thesis (MScMed)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available online.