Thesis--Groningen. / In Periodical Room.

Afhandling (M.D.)--Copenhagen. / Summary in English and Danish. Bibliography: p. [101]-114.

Neuronal histamine(HA) may play a role in memory processing. This hypothesis is based upon evidence that the action of histamine at central H1 and H2 histamine receptor sites has been shown to modulate memory of rats and mice in adversely-motivated tasks. The purpose of this study was to test this hypothesis more thoroughly in mice using two distinct approaches to neuronal HA manipulation. One approach involved the use of new pharmacological agents which act at the histamine H3 receptor. It has been demonstrated that the selective H3 antagonist thioperamide increases HA release in the brain of mice whereas the H3 agonist imetit decreases HA release via modulation of presynaptic H3 autoreceptors. It was expected that an increase in neuronal HA via the autoreceptor mechanism would result in facilitation of memory processing whereas a decrease in HA release would disrupt memory processing. The second approach involved the manipulation of cerebral HA levels via the specific enzyme inhibiting compounds alpha-flouromethylhistidine (alpha-FMH), a potent neuronal HA depleter and metoprine, a histamine-methyl transferase inhibitor which results in accumulation of neuronal HA. Again, effects of increased HA due to metoprine and decreased HA levels due to alpha-FMH were expected to facilitate and disrupt memory processing respectively. One trial inhibitory (passive) avoidance training was employed in each experiment in order to evaluate the effect of each drug on memory. Each compound was tested for effects on memory consolidation and memory retrieval as well as for the presence of state dependent effects. The pattern of effects obtained with thioperamide suggested facilitation of acquisition or memory storage (consolidation) processes, with no effect on the retrieval phase of memory processing. In accordance with those findings, significant disruption of memory occurred when imetit was present during the consolidation phase of memory processing, but not when presented prior to the retrieval phase. These findings suggest that H3 receptor sites play a significant role in the modulation of memory processes via some mechanism which exclusively affects the acquisition or memory consolidation process, while the retrieval of previously laid down memory traces is unaffected.

Thesis ((Hons) M. Sc.)--University of Adelaide, Dept of Clinical and Experimental Pharmacology, 1984. / Mounted illus. Includes bibliographical references (16 unnumbered leaves at end of vol).

Call number: LD2668 .T4 1955 L96 / Master of Science

No description available.

No description available.

Call number: LD2668 .T4 1951 M53 / Master of Science

The importance of chemical cues in triggering the settlement of marine invertebrate larvae has long been recognised but very few such cues have been definitively identified. Larvae of the Australian sea urchin Holopneustes purpurascens, which lives enmeshed in the fronds of macroalgae, are induced to settle by a water-soluble cue produced by the host alga Delisea pulchra. This cue was previously identified as a floridoside-isethionic acid complex. I present evidence in this thesis which supports histamine as the true settlement cue for larval H. purpurascens. The settlement cue was isolated from the polar extract of D. pulchra by bioassay-guided cation-exchange chromatography and identified as histamine using nuclear magnetic resonance spectroscopy. Algal derived and synthetic histamine at ~5 ??M induced rapid settlement in 80???100 % of larval H. purpurascens. In the first study of its kind for any marine invertebrate, variation in the distribution of new recruits was compared with quantitative variation in the distribution of histamine in the habitat. More than 90 % of new recruits were found on either the foliose red alga D. pulchra or on coralline turf algae. These algae induced &gt90 % settlement of larvae in laboratory assays after 24 h. D. pulchra contained far higher levels of histamine than all other algae, however, the coralline algae lacked measurable histamine. Seawater collected in situ adjacent to D. pulchra induced up to 16 % settlement of older larvae and contained the highest concentration of histamine (~5 nM). With the exception of coralline algae, variation in settlement and recruitment was consistent with the variation among species histamine contents. Initial results supported a biofilm derived settlement cue from coralline algae. I also showed that older H. purpurascens larvae settle in response to lower concentrations of histamine than younger larvae and required less exposure to histamine (10 ??M) in order to initiate irreversible metamorphosis. Histamine induced settlement of two other echinoids with non-feeding larvae. Histamine did not induce settlement of feeding larvae of two echinoids or settlement of non-feeding larvae of asteroids. Histamine may be a general settlement cue for echinoids with direct development.

Diss.--Faculty of mathematics and natural sciences--Åbo akademi university, 2001. / Bibliogr. en fin de chap.