RESUMEN
Several lines of evidence suggest a link between the alpha7 neuronal nicotinic acetylcholine receptor (nAChR) and brain disorders including schizophrenia, Alzheimer's disease, and traumatic brain injury. The present work describes a novel molecule, 1-(5-chloro-2,4-dimethoxy-phenyl)-3-(5-methyl-isoxazol-3-yl)-urea (PNU-120596), which acts as a powerful positive allosteric modulator of the alpha7 nAChR. Discovered in a high-throughput screen, PNU-120596 increased agonist-evoked calcium flux mediated by an engineered variant of the human alpha7 nAChR. Electrophysiology studies confirmed that PNU-120596 increased peak agonist-evoked currents mediated by wild-type receptors and also demonstrated a pronounced prolongation of the evoked response in the continued presence of agonist. In contrast, PNU-120596 produced no detectable change in currents mediated by alpha4beta2, alpha3beta4, and alpha9alpha10 nAChRs. PNU-120596 increased the channel mean open time of alpha7 nAChRs but had no effect on ion selectivity and relatively little, if any, effect on unitary conductance. When applied to acute hippocampal slices, PNU-120596 increased the frequency of ACh-evoked GABAergic postsynaptic currents measured in pyramidal neurons; this effect was suppressed by TTX, suggesting that PNU-120596 modulated the function of alpha7 nAChRs located on the somatodendritic membrane of hippocampal interneurons. Accordingly, PNU-120596 greatly enhanced the ACh-evoked inward currents in these interneurons. Systemic administration of PNU-120596 to rats improved the auditory gating deficit caused by amphetamine, a model proposed to reflect a circuit level disturbance associated with schizophrenia. Together, these results suggest that PNU-120596 represents a new class of molecule that enhances alpha7 nAChR function and thus has the potential to treat psychiatric and neurological disorders.
Asunto(s)
Agonistas Colinérgicos/química , Agonistas Colinérgicos/farmacología , Receptores Nicotínicos/metabolismo , Acetilcolina/farmacología , Estimulación Acústica/métodos , Regulación Alostérica , Anfetamina/farmacología , Animales , Animales Recién Nacidos , Calcio/metabolismo , Línea Celular , Estimulantes del Sistema Nervioso Central/farmacología , Antagonistas Colinérgicos/farmacología , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Estimulación Eléctrica/métodos , Células Epiteliales/efectos de los fármacos , Potenciales Evocados Auditivos/efectos de los fármacos , Hipocampo/citología , Humanos , Técnicas In Vitro , Isoxazoles/química , Isoxazoles/farmacología , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Potenciales de la Membrana/efectos de la radiación , Microinyecciones/métodos , Neuronas/efectos de los fármacos , Neuronas/fisiología , Nicotina/farmacología , Oocitos , Técnicas de Placa-Clamp/métodos , Compuestos de Fenilurea/química , Compuestos de Fenilurea/farmacología , Subunidades de Proteína/fisiología , Ratas , Ratas Sprague-Dawley , Tetrodotoxina/metabolismo , Factores de Tiempo , Xenopus , Receptor Nicotínico de Acetilcolina alfa 7RESUMEN
Four dopamine receptor agonists used for the treatment of Parkinson's disease (apomorphine, pergolide, ropinirole and sumanirole) were evaluated for the ability to block human ether-a-go-go related gene (hERG) K(+) channels and to modify the duration of canine Purkinje fiber action potentials. Apomorphine, pergolide and ropinirole blocked the hERG-mediated currents with IC(50) values of 2.4, 0.12 and 1.2 microM, respectively. When evaluated in an action potential duration assay, pergolide significantly shortened action potential duration at 90% repolarization (APD(90)) whereas apomorphine and ropinirole significantly prolonged repolarization. Sumanirole only partially blocked hERG K(+) channels at the highest tested concentration (10 microM) and did not modify action potential duration over the tested concentration range (0.65-65 microM). Taken together, these data provide evidence that dopamine receptor agonists developed for the treatment of Parkinson's disease differentially influence hERG K(+) channel function and cardiac action potential duration.