Title: Apamin blocks certain neurotransmitter-induced increases in potassium permeability.

Authors: B E Banks, C Brown, G M Burgess, G Burnstock, M Claret, T M Cocks, D H Jenkinson

Journal, date & volume: Nature, 1979 Nov 22 , 282, 415-7

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/228203

Abstract
Apamin is a neurotoxic polypeptide of known structure isolated from bee venom. Shuba and coworkers have recently shown that it abolishes the hyperpolarising action of externally-applied ATP on visceral smooth muscle (guinea pig stomach and taenia coli) as well as the hyperpolarisation (inhibitory junction potential) that follows stimulation of the non-adrenergic inhibitory nerve supply to these tissues. As it has been proposed that ATP is the neurotransmitter involved in the latter response, Vladimirova and Shuba tentatively concluded that apamin is a specific postsynaptic blocking agent of this non-adrenergic, possibly 'purinergic', inhibition. We have confirmed the important observation that nanomolar concentrations of apamin reduce inhibition by ATP and by non-adrenergic nerve stimulation, but further experiments suggest that, rather than acting as a specific blocker of ATP receptors, apamin inhibits the increase in potassium permeability caused by a number of agents, including ATP.