RESUMEN
The influence of low temperature results in the activation of a sympathetic division of the vegetative nervous system (mostly alpha2-artery adrenoreceptors). The data concerning the tone of the parasympathetic department are inconsistent. In studies carried out in experimental animals (rabbits), the cholinoreactivity of arterial vessels was investigated. After a single cooling the depressing action of acetylcholin on arterial vessels grows only because of an increase of the quantity of active (Pm) M-cholinoreceptors of vessels (by 66.6%) with a decrease of their sensitivity (1/K = 4) by 33.3%. By day 30 of cold depressing adaptation the action of acetylcholin grows (with doses 0.02-0.1 mkg/kg) only because of an increase of M-cholinoreceptors sensitivity by 233%. The reduction of the depressing action on arteries of acetylcholin with dozes of 0.2-0.8 mkg/kg is explained by a decrease of the quantity of active M-cholinoreceptors in these terms of the cold influence (by 41% as compared with a control group). According to the results the efficiency of the interaction (E = (Pm/2)*R)) of acetylcholin with M-cholinoreceptors of vessels grows by 96% (with E = 300 mm/m.c./1 mkg/kg in a control group up to E = 588 after 30 day's adaptation to cold).