n(6)-cyclopentyladenosine and Poisoning

To study the therapeutic efficacy and mechanism of adenosine receptor agonist N(6)-cyclopentyladenosine (CPA) against acute dichlorvos poisoning.. Soon after a certain doses of dichlorvos were given to mice and rats by gastrogavage, physiological saline, CPA, atropine or pralidoxime chloride were administered to different groups. Toxic signs and survival rate were recorded and cholinesterase (ChE) activities and acetylcholine (ACh) concentrations in whole blood were determined in treatment group with CPA and non-treatment group after dichlorvos was given to rats by gastrogavage.. (1) The alleviated and delayed appearance of toxic signs as well as obvious prolongation of survival time was observed in CPA treatment group compared with non-treatment group. (2) ChE activities in both treatment group with CPA [(0.49 +/- 0.05) U/ml] and non-treatment group [(0.52 +/- 0.04) U/ml] were significantly lower than that [(1.56 +/- 0.15) U/ml] of the control group (P < 0.01), but there was no significant difference between treatment group and non-treatment group (P > 0.05). (3) ACh concentration [(204.24 +/- 20.48) microg/ml] in whole blood of treatment group with CPA was significantly lower than that [(230.91 +/- 25.61) microg/ml] of non-treatment group (P < 0.05).. CPA has therapeutic efficacy against acute dichlorvos poisoning, which is probably through the decrease in ACh concentration.

Topics: Acetylcholine; Acute Disease; Adenosine; Animals; Cholinesterases; Dichlorvos; Insecticides; Male; Mice; Mice, Inbred Strains; Poisoning; Purinergic P1 Receptor Agonists; Rats; Rats, Sprague-Dawley

Mortality and occurrence of cholinergic symptoms upon sarin intoxication (144 micro g/kg s.c., approximately 2 x LD50) in rats is completely prevented by treatment with the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA, 2 mg/kg i.m.). Previously, we have shown that CPA treatment altered the distribution of sarin into the brain, presumably through its cardiovascular side effects. Therefore, the objective of the present study was to evaluate the contribution of the cardiodepressant effects of CPA to its therapeutic efficacy against sarin intoxication. Intramuscular treatment of rats with 0.5 and 2.0 mg/kg CPA 1 min after sarin poisoning attenuated most cholinergic symptoms and prevented mortality, which seemed to be directly associated with an immediate strong and long-lasting bradycardia and hypotension caused by CPA. Treatment with lower doses of CPA (0.1 and 0.05 mg/kg i.m.) caused similar levels of bradycardia and hypotension, albeit a few minutes later than at the higher doses of CPA. Upon sarin intoxication, this was correlated with increased incidence of cholinergic symptoms and decreased survival rates. Pretreatment with the peripheral adenosine A1 receptor antagonist 8- p-sulphophenyltheophylline (8-PST, 20 mg/kg i.p.) counteracted the cardiodepressant effects of 0.05 mg/kg CPA almost completely, thereby nearly abolishing its therapeutic efficacy against sarin poisoning. In conclusion, the present results strongly indicate that bradycardia and hypotension induced by the peripheral adenosine A1 receptor play a prominent role in the therapeutic efficacy of CPA in cases of sarin poisoning.

Topics: Adenosine; Animals; Bradycardia; Chemical Warfare Agents; Dose-Response Relationship, Drug; Drug Antagonism; Drug Therapy, Combination; Heart Diseases; Hypotension; Injections, Intramuscular; Male; Poisoning; Purinergic P1 Receptor Agonists; Rats; Sarin; Theophylline