RESUMEN
The large diversity of peptides from venomous creatures with high affinity for molecules involved in the development and maintenance of neuropathic pain has led to a surge in venom-derived analgesic research. Some members of the α-conotoxin family from Conus snails which specifically target subtypes of nicotinic acetylcholine receptors (nAChR) have been shown to be effective at reducing mechanical allodynia in neuropathic pain models. We sought to determine if three such peptides, Vc1.1, AuIB and MII were effective following intrathecal administration in a rat neuropathic pain model because they exhibit different affinities for the major putative pain relieving targets of α-conotoxins. Intrathecal administration of α-conotoxins, Vc1.1, AuIB and MII into neuropathic rats reduced mechanical allodynia for up to 6 h without significant side effects. In vitro patch-clamp electrophysiology of primary afferent synaptic transmission revealed the mode of action of these toxins was not via a GABA(B)-dependent mechanism, and is more likely related to their action at nAChRs containing combinations of α3, α7 or other subunits. Intrathecal nAChR subunit-selective conotoxins are therefore promising tools for the effective treatment of neuropathic pain.
Asunto(s)
Conotoxinas/metabolismo , Neuralgia/metabolismo , Subunidades de Proteína/metabolismo , Receptores Nicotínicos/metabolismo , Animales , Animales Recién Nacidos , Conotoxinas/administración & dosificación , Inyecciones Espinales , Masculino , Neuralgia/tratamiento farmacológico , Técnicas de Cultivo de Órganos , Subunidades de Proteína/agonistas , Ratas , Ratas Sprague-Dawley , Receptor Nicotínico de Acetilcolina alfa 7RESUMEN
The synthetic alpha-conotoxin Vc1.1 is a small disulfide bonded peptide currently in development as a treatment for neuropathic pain. Unlike Vc1.1, the native post-translationally modified peptide vc1a does not act as an analgesic in vivo in rat models of neuropathic pain. It has recently been proposed that the primary target of Vc1.1 is the alpha9alpha10 nicotinic acetylcholine receptor (nAChR). We show that Vc1.1 and its post-translationally modified analogs vc1a, [P6O]Vc1.1, and [E14gamma]Vc1.1 are equally potent at inhibiting ACh-evoked currents mediated by alpha9alpha10 nAChRs. This suggests that alpha9alpha10 nAChRs are unlikely to be the molecular mechanism or therapeutic target of Vc1.1 for the treatment of neuropathic pain.