Effect of Philanthotoxin on Neuromuscular Transmission of Tick (Rhipicephalus appendiculatus)

Neuromuscular transmission is a main target site for the chemical control of many pests. L-glutamate mediates synaptic excitation at neuromuscular junction in arthropods and regulates skeletal muscle activity. Polyamine amides regulate cell excitability in the neuromuscular system of arthropods. Philanthotoxin (PhTX) and its analogues block the glutamate receptors which are involved in arthropod neuromuscular transmission. In this study the action of synthetic analogues (PhTX-343, C7-PhTX-343, DNP12-PhTX-343) of PhTX-433 which is an open ion channel blocker were examined on evoked excitatory postsynaptic potential (EPSP) in tick coxal muscle. These compounds all antagonized the evoked EPSP in a use-dependent manner. The tick nerve-muscle preparation has proved to be useful for providing an insight into the numerous and complex interactions that occur between philanthotoxin and glutamate neurotransmission. Philanthotoxin interacts with the open ion channel of GluRs and is potentially useful for the isolation of excitatory amino acid receptors from excitable tissue and for the development of novel pesticides.