A specific prostaglandin E_2 (PGE_2) receptor has been identified in the salivary glands of female lone star ticks, Amblyornma amencanum (L). The receptor is linked to a guanine nudeotide (G) protein and activates a phosphoinositide phospholipase C signalling pathway increasing the inositol trisphosphate level and mobilising intracellular Ca~(2+). Low concentrations of PGE_2 stimulate secretion of anticoagulant proteins by dispersed salivary gland acini. We hypothesise that, after the initial stimulation of salivary glands by dopamme, the PGE_2 formed mobilises Ca~(2+) and results in the secretion (exocytosis) of bioactive proteins into the saliva during tick feeding.
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