Cardiac beta-receptor variation in rat strains selectively bred for differences in susceptibility to stress.

The radioligand 3H-DHA was used to estimate the density and affinity of cardiac beta-receptors in rat strains selectively bred for differences in response to stress. Maudsley Reactive rats selected for heightened reactivity to stress had a greater density of beta-adrenergic binding in cardiac membranes than rats of two genetically distinct Maudsley Non-Reactive strains selected for decreased reactivity to stress, and compared with one of these Non-Reactive strains the MNR/Har, increased affinity for 3H-DHA. Together with previous findings the present results demonstrate a negative correlation between estimates of basal sympathetic activity on the on hand, and post-synaptic beta-receptors in heart on the other, that are consistent with the notion that these receptor alterations have occurred as a result of long-term differences in pre-synaptic release of transmitter. The Maudsley strains may, therefore, provide a useful model for the study of beta-adrenergic receptors as a physiological locus for regulation of end-target responsiveness to sympathetic stimulation.