The binding of a novel GABAs receptor radioligand eH]-CGP62349 to human hippocampal control and epileptic sections was investigated using quantitative receptor autoradiography. Kinetic analyses performed on rat brain sections, to conserve the use of human tissues, demonstrate that eH]-CGP62349 associated rapidly. The same radioligand dissociated rapidly initially, then very slowly. Utilising human hippocampus it was shown that CH]-CGP62349 bound with high affinity (O.SnM) to human control hippocampal sections. The kinetics of GABAs receptor in human hippocampus using the novel compound confirmed previous studies performed in rat membrane. The localisation of GABAB receptors in human hippocampal control partially supported former studies using agonist ligands such as CH]-GABA and eH]-baclofen, despite differences have been noticed. Hippocampal slices from surgical resected specimens obtained from hippocampal sclerotic (HS)/temporal lobe epilepsy (TLE) patients were compared with neurologically normal post-mortem control subjects for neuropathology and GABAs receptor density and affinity. Neuronal loss was observed in most of the hippocampal subregions, whereas in subiculum any significant difference was detected. For GABAa receptor density (Bmax) a significant reduction was reported in CA3, CA4, and DG; the affinity was increased exclusively in DG. After the correction of Bmax value for the neuronal loss a significant increase was seen in CA3. Oligonucleotides were designed to investigate the two GABAB1 isoforms (la, and lb), and the GABAa2 subunit in human hippocampal control and HSITLE tissues, obtained as well as for the autoradiography. GABAsla, GABAB1b, and GABAB2 transcript distribution was in agreement with the receptor protein localisation, even though in the human hippocampus GABAa2 has to be yet localised and to verify if it is associated with GABAsla or GABABlbto form the dimeric active receptor. The present study suggests an involvement of GABABreceptors in HS/TLE in some not all the hippocampal subregions in terms of receptor density and affinity. Further investigations in regard to the quantitative in situ hybridisation data and the immunocytochemical results are fundamental to gain insight into the pathological role of GABAs receptors.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:289300 |
| Date | January 2003 |
| Creators | Princivalle, Alessandra Patrizia |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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