Nowadays problems of direct impact of melatonin upon the nervous, endocrine, immune system activity as well as the state of hemostasis either in normal or in pathological condition are being widely discussed. This survey is supposed to study the impact of the melatonin medicine "Melaxen" on the platelet link of hemostasis in the experimental conditions. The test was carried out within the winter-spring period on 40 white sexually-mature male rats, kept in a standard vivarium conditions with the interchange of natural and artificial light in order to exclude the impact of endogenous melatonin upon the hemostasis through the blocking of its synthesis. Under the affection of maximum and minimum doze of erythrocyte hemolysate the platelet aggregate activity (PAAm and PAAs) and platelet activity index (PAI) were estimated according to the results of the hemolysate-aggregation test. The experimental disfunction of platelets mdelling was carried out via peroral introduction of aspirin in doze of 500 mg/kg to the animals of the second group. Within the third and the fourth group against the background of melaxen that was introduced in the course of a week in doze of 0,1 mg/kg and 10 mg/kg accordingly, the aspirin was introduced 24 hours before the test. The rats of the first group were kept in the standard vivarium conditions without any medical preparations.

The PAAm was 90,9±20,4%, the PAAs was ,4±5,69%, while the PAI was 4,73±1,22 within the check group. Under the affection of acetylsalicinic acid at the expence of full tromboxane system blocking the blood plates aggregation ability was absolutely missed. However, the preliminary introduction of melaxen allowed us to significantly reduce the aspirin effect. The PAAm was raised up to 5,0±17,7%, and the PAAs - up to 146,5±18,9%. The PAI was 3,72±0,63. The AATm within the fourth group animals was about 98,3±8,31%, while the AAPs index significantly exceeded the control point and made 255,7±14,4%, but PAI was close to control point (4,16 ±0,5).

Thus, we can see that melatonin has a direct impact on the platelet link of hemostasis. Against its background blood plates conserve their aggregation process ability under the affection of antiaggregant. This effect is dependent on the doze of melaxen.

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The article was presented for the international scientific conference "The modern problems of experimental and clinic medicine", Thailand (Bangkok-Pattaya), 20-30^th of December 2009. Received by editorial office on 11.14.2009.