RESUMO
Kainic acid (KA)-sensitive glutamate sites have been investigated by receptor autoradiography and in situ hybridisation histochemistry (ISHH) to evaluate their relationship to specific high-affinity KA receptors identified in molecular biological studies. Autoradiography with [3H]KA in the presence of the AMPA-selective antagonist NBQX (1 microM) revealed a widespread distribution of receptors through brain, especially in neocortex, hippocampal CA3, corpus striatum and granule cell layer of cerebellum. Specific binding was insensitive to the AMPA-selective agonist, S-5-fluorowillardiine, but inhibited by kainoids in a manner suggestive of receptor heterogeneity. Expression of the KA-2 receptor subunit mRNA by ISHH was also localised in hippocampal CA3 and cerebellar granule cells, suggesting some high-affinity native KA receptors labelled by [3H]KA were likely to include the KA-2 subunit in their heteromeric assembly.
Assuntos
Química Encefálica/fisiologia , Encéfalo/anatomia & histologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Receptores de Ácido Caínico/efeitos dos fármacos , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/farmacologia , Alanina/análogos & derivados , Alanina/farmacologia , Animais , Autorradiografia , Sequência de Bases , Química Encefálica/efeitos dos fármacos , Técnicas In Vitro , Masculino , Dados de Sequência Molecular , Pirimidinonas , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/agonistas , Receptores de Ácido Caínico/genética , UracilaRESUMO
The characteristics and localization of high-affinity, kainic acid (KA)-sensitive glutamate sites have been investigated using a radioreceptor procedure to provide insights into specific high-affinity KA receptors identified in molecular biological studies. Binding sites identified by employing [3H]KA. in the presence of the AMPA-selective antagonist NBQX (1 microM), and slide-mounted, coronal sections of rat cerebellum were of high-affinity (Kd 6 nM) and possessed an unique pharmacological profile. Specific binding was to a single population of sites and fully inhibited by kainoids and glutamate, but essentially insensitive to AMPA and willardiines. Autoradiography revealed that the high-affinity KA sites were localized to the granule cell layer of cerebellum. The KA site resembled both the KA receptor found on spinal motoneurones and the KA-2 type of receptor.
Assuntos
Cerebelo/metabolismo , Ácido Caínico/metabolismo , Receptores de Ácido Caínico/metabolismo , Animais , Autorradiografia , Ligação Competitiva , Cerebelo/citologia , Relação Dose-Resposta a Droga , Ácido Glutâmico/farmacologia , Ácido Caínico/análogos & derivados , Ácido Caínico/farmacologia , Cinética , Masculino , Quinoxalinas/farmacologia , Ácido Quisquálico/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/antagonistas & inibidores , Receptores de Ácido Caínico/análise , TrítioRESUMO
A series of mono- and dicationic derivatives of various di- and triazaphenanthrenes were synthesized and evaluated against both wild-type and amsacrine-resistant P388 leukemia in vitro. Monocationic derivatives of the fully-aromatic benzo[c][1,8]naphthyridine chromophore showed moderate and equal cytotoxicity in both cell lines, suggestive of efficacy against both the alpha and beta isozymes of mammalian DNA topoisomerase II. Derivatives of both the benzo[c][1,8]naphthyridine and benzo[c][1,8]naphthyridine-3(4H)-one chromophores also showed significant in vivo activity against wild-type P388 leukemia.
