The authors studied the responsiveness of cardiac beta-receptors to isoproterenol, a noradrenergic agonist, in 29 depressed patients and 13 control subjects. They showed a significantly lower sensitivity in depressed patients as compared with the control subjects. Focussing on the group of depressed patients without antidepressant treatment in the month preceding the study (n = 15) in order to avoid a bias, the following significant results were obtained: cardiac beta-adrenergic receptor sensitivity was lower in patients suffering from endogenous depression than in those suffering from reactive depression (as classified by Newcastle Scale). There was a negative linear relation between cardiac beta-adrenergic sensitivity and the posttreatment clinical state (as expressed by the MADRS score) for the 9 patients who ended a 3-week desipramine treatment period.

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