Characterization of levamisole binding sites in Trichinella spiralis

Characterization of the levamisole receptor was performed with total extracts of Trichinella spiralis muscle larvae using binding assays with tritiated levamisole ([3H]LEV, 291 GBq/mmol). We detected a specific [3H]LEV binding activity with a dissociation constant (Kd) of 4.76 μM and a receptor density (Bmax) of 2.14 pmol/mg of protein. In inhibition studies, only dimethylphenylpiperazinium iodide (DMPP) and hexamethonium were found to be competitive inhibitors of the [3H]LEV binding with an inhibition constant (Ki) of 31.04 and 4.43 μM, respectively, whereas d-tubocurarine and α-bungarotoxine had no effect on [3H]LEV binding activity, and procaine and atropine potentiated the [3H]LEV-receptor binding. All these data support the idea that levamisole acts as a cholinergic agonist in T. spiralis.