[Changes in the sensitivity of the alpha 2- and beta 1-adrenoreactive systems during the intensive cooling of rats acclimatized to cold].

Cold-acclimated rats with an increased resistance against intensive cold, differ from ordinary animals by increased beta 1- and decreased alpha 2-adrenoreactivity in ordinary conditions; their beta 1-adrenoreactive systems preserve sensitivity at intensive cold exposure (up to hypothermia below 25 degrees C), whereas the sensitivity of their alpha 2-adrenoreactive systems declines more rapidly (up to a moderate hypothermia--33-34 degrees C). The data obtained suggest the described shifts to be important for essential increase in general resistance against acute intensive cold exposure in rats.