K+ channel sub-types in rat brain: Characteristic locations revealed using β-bungarotoxin, α- and δ-dendrotoxins
1991; Elsevier BV; Volume: 40; Issue: 1 Linguagem: Inglês
10.1016/0306-4522(91)90172-k
ISSN1873-7544
Autores Tópico(s)Nicotinic Acetylcholine Receptors Study
ResumoSub-types of fast-activating, voltage-dependent K+ channels were localized in rat brain using the specific probe, α-dendrotoxin, in conjunction with the putative K+ channel ligands, δ-dendrotoxin and β-bungarotoxin. Sheet-film autoradiography of brain sections labelled with radioiodinated α-dendrotoxin showed that its acceptors occur in most synapse-rich and gray matter regions, and nerve tracts; all of this labelling was abolished by α-dendrotoxin or its homologue, toxin I. Other structurally related peptides from mamba snake venom, β- and γ-dendrotoxin, were much less effective in preventing γ-dendrotoxin labelling. In common with the sites for α-dendrotoxin and β-bungarotoxin, γ-dendrotoxin acceptors were enriched in cerebral cortex, thalamus and molecular layer of both the cerebellum and dentate gyrus of the hippocampus. However, γ-dendrotoxin failed to show significant binding to the Purkinje cell layer of the cerebellar cortex and stratum lacunosum moleculare of the hippocampal formation, areas labelled prominently by the other two probes. Evidence of this apparent heterogeneity in the toxin-binding proteins was consolidated by the observed inability of γ-dendrotoxin to inhibit125I-labelled α-dendrotoxin or β-bungarotoxin binding to these specified regions. Thus, γ-dendrotoxin, like β-bungarotoxin, discriminates between sub-types of α-dendrotoxin acceptors but in different fashions. Whilst β-bungarotoxin interacts preferentially with a sub-population in synaptic areas, γ-dendrotoxin distinguished sub-types in certain synaptic and gray matter regions and, in this, resembles mast cell degranulating peptide, a ligand known to block an α-dendrotoxin-sensitive K+ current.
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