The MDR-1 (Multi-Drug Resistance) gene is encoding the P-glycoprotein. In the blood brain barrier the P-glycoprotein is actively exporting the toxic compounds out of the brain to avoid the accumulation of them in the brain tissue. The MDR-1 mutant individuals cannot express P-glycoprotein, consequently the toxic substances are accumulated in brain tissue and causing poisoning.

The hereditary MDR-1 gene defect was detected in many species even in human beings. Nonetheless, it occurs very frequently in certain dog breeds, such as Collie, Bobtail, German-, English- and Australian Shepherd. According to literature data the occurrence of MDR-1 mutation can reach up to 30% in certain dog populations. The susceptible purebred individuals and their mixtures show serious poisoning symptoms (ataxia, languor, seizures) after administration of safe drugs used in veterinary medicine. These drugs that are frequently used in veterinary practice e.g. ivermectin, loperamide, doxorubicin, cyclosporine, digoxin, acepromazine, butorphanol and many other compounds. The affected dogs often die in spite of the symptomatic treatment.

During our investigations blood samples are collected from the largest possible population of dog breeds concerned. In the genetic testing; DNA isolation from blood samples followed by allele specific detection of MDR-1 mutation via PCR method will be performed.