The mechanism of the antidepressant action of electroconvulsive therapy (ECT) remains unknown. Based on previous work with antidepressant drugs and their effects on the noradrenergic system, we undertook this study to further determine the effects of ECT on selected indices of peripheral adrenoceptor function in depressed patients.
Binding parameters (Bmax and Kd) of platelet
α2- and leukocyte β2-adrenoceptors, plasma noradrenaline (NA), 3-methoxy-4-hydroxy-phenylglycol (MHPG) and cortisol levels were determined in 18 patients, prior to treatment and 14 days after the last of a series of ECTs, and compared with samples obtained from 18 matched control subjects. Results
α2-adrenoceptor sites were significantly elevated in untreated patients compared with controls ( P< 0.03), but leukocyte β2-adrenoceptor numbers did not differ. Treatment with ECT led to a significant reduction in platelet α2-adrenoceptor numbers, whereas leukocyte β2-adrenoceptor densities increased. Pre-ECT plasma NA, MHPG, and cortisol levels were elevated in patients, compared with controls, and decreased following ECT, but these differences were not statistically significant. Post-ECT plasma NA and β2-adrenoceptor numbers were significantly, negatively correlated ( P< 0.05). Conclusions
These results suggest that platelet
α2-adrenoceptors are supersensitive in depressed patients and treatment with ECT results in down-regulation of these receptors, which may be interpreted as a primary therapeutic, ‘normalising’ effect. The post-ECT changes in leukocyte β2-adrenoceptors are probably only secondary to the lower circulating plasma NA levels.