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Antibody technology was applied to the study of synaptic plasticity resulting from passive avoidance training in the chick and long-term potentiation in the rat. These studies fell into three categories: 1) the disruption of memory for a one-trial passive avoidance task by intracranial injection of an anti-postsynaptic density antiserum 2) mapping time- and locus-specific changes in the chick brain using antisera to the cytoskeletal proteins (Xtubulin and microtubule-associated protein 2 following passive avoidance training and 3) using antibodies to synaptically-enriched antigens to map time- and locus-specific changes in hippocampal subfields following long-term potentiation in the rat. In the first series of experiments an antiserum (RI4) was raised against protein from chick forebrain postsynaptic densities (PSDs). The antiserum was characterised and was found to recognise six distinct antigens as determined by Western Blots. These antigens were found to have a primarily (but not exclusively) synaptic location. Intracranial injections of IgG isolated from R14 resulted in amnesia for a one-trial passive avoidance paradigm in the chick when administered 60min pre-training (but not 30min or 15min pre-training or 1000n post-training), in chicks tested 24hrs (but not Ihr or 3hrs) post-training. In the second set of experiments monoclonal antibodies were used to examine changes in levels of the cytoskeletal proteins a-tubulin and microtubule-associated protein 2 (MAP2) in specific forebrain loci following passive avoidance training in the chick. Of the regions examined, elevations in the titre of anti-a-tubulin were found in the left Intermediate Hyperstriatum Ventrale (IMHV) l hr, 6hrs and 24hrs following passive training, in the left Lobus Parolfactorius (LPO) 1hr following training and in the right LPO 6hrs and 24hrs following training. A hemispherically-asymmetrical change was found in the titre of anti-MAP2 which was interpreted as possibly reflecting a decrease in the amount of the antigen in the left IMHV 24hrs following training. No training-related changes were detected, using either antibody, in a third forebrain region, the Paleostriatum Augmentatum (PA). During the characterisation of antiserum R14 it was found that only one antigen (with an apparent molecular weight of 230kDa) is conserved between the chick and rat brain. The antigen is enriched in synaptic fractions isolated from the rat hippocampus and was used, as well as a PSD-specific monoclonal antibody, 411B, to examine possible changes in hippocampal subfields CAl, CA3 and the dentate area taken at several time-points following tetanisation of the right perforant path. 24hrs following tetanisation (but not at earlier time-points), the titre of R14 was elevated in the dentate area ipsilateral to tetanisation and in both the ipsi- and contralateral CAL The titre of 411B was increased specifically in the target, dentate area and only at 8hrs following tetanisation, an increase which was abolished in the presence of the protein synthesis inhibitor, anisomycin. These results are discussed in the context of current models of synaptic plasticity.

An ultra-low dose of a drug is approximately 1000-fold lower than the dose range traditionally used to induce a therapeutic effect. The purpose of the present thesis was to broaden the knowledge of the ultra-low dose effect, that was previously identified in the opioid receptor system, by looking at whether opioids and cannabinoids interact at the ultra-low dose level, whether cannabinoid receptors themselves demonstrate the ultra-low dose antagonist effect, and whether the opioid ultra-low dose effect is maintained in a model of persistent, unavoidable pain. For experiment 1, separate groups of Long Evans rats were tested for antinociception following an injection of vehicle, the cannabinoid agonist WIN 55 212-2 (WIN), the opioid antagonist naltrexone (an ultra-low or a high dose), or a combination of WIN and naltrexone doses. Ultra-low dose naltrexone elevated WIN-induced tail flick thresholds without extending its duration of action. In experiment 2, antinociception was tested in rats following either acute or sub-chronic (7 days) injections of vehicle, WIN, ultra-low doses of the CB1 receptor antagonist rimonabant (SR 141716), or a combination of WIN and ultra-low dose rimonabant. Following the chronic experiment, striatal tissue was rapidly extracted and subjected to co-immunoprecipitation to analyse CB1 receptor coupling to G-protein subtypes. Ultra-low dose rimonabant extended the duration of WIN-induced antinociception, and attenuated the development of WIN-induced tolerance. Animals chronically treated with WIN alone had CB1 receptors predominately coupling to Gs proteins, whereas all other groups had CB1 receptors predominately coupling to Gi proteins. For experiment 3, all animals were subjected to the formalin test following either acute or sub-chronic injections of vehicle, the opiate morphine, ultra-low doses naltrexone, or a combination of morphine and ultra-low dose naltrexone. Ultra-low dose naltrexone had no significant effect on morphine-induced pain ratings in either the acute, or sub-chronic drug treatments. This thesis provides evidence that the ultra-low dose effect, including the agonist-induced G-protein coupling switch, extends to another receptor type. This effect may, therefore, be part of a generalized principle that applies to many G-protein coupled receptors. / Thesis (Ph.D, Psychology) -- Queen's University, 2007-11-05 09:31:30.162 / A portion of this research was supported by a Canadian Institutes of Health Research (CIHR) Proof of Principle Grant to M.C. Olmstead and J.J. Paquette.