Pharmacological studies on the molluscicidal activity of phorate on Pila globosa (Gastropoda).

Amongst heart, rectum and radula protractor muscles of Pila globosa, the heart showed a negative inotropic and negative chronotropic response while the rectum and radula protractor showed a positive tonotropic response to exogenously applied acetycholine (ACh). The anti-cholinesterase pesticide phorate substantially increased the response to ACh; at high doses it could also evoke cholinomimetic response from the heart. The anti-cholinesterase property of phorate gradually increased with an increase in its contact period to the tissue. The extent of alteration in ACh response caused by prior treatment with low and high doses of phorate were very similar, indicating that the efficacy of phorate is by and large time-dependent rather than dose-dependent. The effect of phorate remained irreversible even after prolonged washing. The mode of action of phorate has been discussed in the light of the above findings.