Changes in brain alpha-adrenoceptors with increasing age in rabbits.
The effects of aging on rabbit brain alpha-adrenoceptor number was studied using radioligand binding techniques. The ligands [3H]prazosin and [3H]clonidine were used to examine binding to alpha 1 and alpha 2-adrenoceptors, respectively, in forebrain and hindbrain membranes from rabbits aged from 1 month to 3 years. Changes in specific [3H]clonidine binding were compared to changes in central alpha 2-adrenoceptor function as measured by the fall in blood pressure after intracisternal administration of clonidine. Both alpha 1- and alpha 2-adrenoceptor number decreased with age in the rabbit brain. The maximum fall in specific [3H]prazosin binding occurred in animals aged between 3 and 6 months. [3H]clonidine binding in forebrain was also reduced in 6-month-old animals but [3H]clonidine binding in hindbrain was only reduced in animals over 2 years old. Despite the reduction in [3H]clonidine binding no decrease in the in vivo response to centrally administered clonidine was observed in 2-year-old animals when compared to 3-month-old rabbits.
D000375:Aging; D000818:Animals; D001794:Blood Pressure; D001921:Brain / Q000378:metabolism*; D003000:Clonidine / Q000378:metabolism; D008297:Male; D011224:Prazosin / Q000378:metabolism; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
D011942:Receptors, Adrenergic, alpha; D003000:Clonidine; D011224:Prazosin