Pharmacological actions of HS-6, an oxime, on the neuromuscular junction

The effect of HS-6 [1-(2-hydroxyiminomethylpyridinium)-1-(3-carboxamidopyridinium)-dimethyl ether] on neuromuscular (NM) transmission was investigated using chick biventer cervicis (CBC), rat diaphragm (RD) and guinea pig ileum longitudinal muscle strip (GPLS) preparations. In the CBC preparation HS-6 did not cause a contraction, whereas it produced a dose-related contraction of the GPLS preparation. HS-6 produced a hemicholinium-like NM blockade in the CBC and RD preparations. This was supported by the fact that HS-6 inhibited choline uptake in erythrocytes. HS-6 inhibited the contractions of various nicotinic agonists in the CBC preparation and augmented the acetycholine contractions. The latter was due to AChE inhibition produced by HS-6.