[Circadian rhythm of plasma norepinephrine in depressive disorders. Preliminary study]

The biological desynchronisation hypothesis of (endogenous) depressive disorders arises from the disturbances in the circadian rhythmicity of several biological functions in depressive illness and clinical improvement during various sleep deprivation processes. Furthermore, supportive evidence exists to postulate a central noradrenergic dysfunction, at least in a sub group of depressive disorders. We studied the 24 h kinetics of plasma norepinephrine in patients suffering from Affective Disorders-Major Depressive Episode according to DSM III criteria. Blood samples were drawn hourly from an indwelling venous catheter in supine subjects. Plasma NE was measured by HPLC with electrochemical detection. 5 patients (age: 35-63) were studied in base line drug free depressive state and compared with 5 control subjects (age: 44-53), then, in 4 patients, on the 8th and 21st days under antidepressant treatment. Control subjects exhibited a circadian rhythm of TP but a weak amplitude and low values during sleep, as previously described. Depressed patients did not display any rhythmicity because of a reduced amplitude and high plasma levels during sleep. Antidepressants did not restore the rhythm. Our results suggest a rhythmic instability involving a circadian lability linked to an ultradian release during sleep. This NA disinhibition could participate in the depressive desynchronisation and the potential relationships with sleep disorders must be discussed.