The objectives of this project are to assess changes in properties (number, affinity) of receptors in response to alterations in the environment, drug administration, stress, or hormones, and to develop methods for assessing receptor function in intact animals, in vivo. Stress or isoproterenol-induced reduction of adrenoceptors can be prevented by administration of quinacrine. The alpha-adrenoceptor mediated pressor responses to administered norepinephrine are of the alpha2 type whereas different alpha1- adrenoceptors (in the junction) respond to norepinephrine released from sympathetic nerves.