a new approach for aggregation of paramecium caudatum by nitric oxide.

background and objective: nitric oxide (no) plays a role in thermoregulation and growth of protozoa. this work aimed to add the molecule no in physiology of protozoa in contact with abused narcotic substances. materials and methods: a sedative drug, morphine, was infused into a cell chamber containing paramecia . the cell response to the drug was recorded promptly after drug infusion using a potency protocol provided for the first time at this laboratory. a precursor of no, l-arginine, was treated jointly with drug to involve the no system in protozoan performance to drug exposure. marking of nadph-diaphorase (nadph-d) was followed to provide data to explain the mechanisms.   results: morphine, particularly 0.5 to 60 μg/μl, aggregated the paramecia . the infusion of l-arginine (1 to 8 µg/µl) together with morphine potentiated this effect, though, pre-usage of l-name (1 to 8 µg/µl), a blocker of no production, reversed the response. notably the activation of nadph-d in solely morphine or l-arginine plus morphine samples was revealed. however, the expression of marker was attenuated upon pre-infusion with l-name. conclusion: this study introduces a new approach to involve no in physiology of aggregation of paramecia following exposure to the misused sedative drug, morphine.