Age-related changes in adrenergic neuroeffector transmission.

In this study we have looked at the effects of ageing on prejunctional control of noradrenergic neurotransmission in the cardiovascular system, in terms of alpha2-adrenoceptors, beta2-adrenoceptors and the noradrenaline re-uptake process. These studies show diminished prejunctional alpha2- and prejunctional beta-adrenoceptor-mediated responsiveness together with diminished noradrenaline re-uptake in rat tissues. The reduced prejunctional alpha2-inhibitory control and reduced re-uptake found in tissues from aged rats is more than likely to outweigh the effects of reduced beta-adrenoceptor facilitation, at least in normal conditions. Hence, assuming that such changes also occur in man, we might expect to find evidence of increased release of noradrenaline from noradrenergic nerves, and this could be reflected in plasma levels of noradrenaline.