Exploration de la fonction dopaminergique dans les dépressions bipolaires et unipolaires

Indirect observations suggest that dopamine function may be altered in depressed patients, notably in bipolar patients. The purpose of this study was to assess the dopamine receptor sensitivity at the hypothalamic-pituitary level in 19 drug-free DSM-IV major depressed patients: 10 bipolar depression (BP), 9 unipolar depression (UP), compared with 15 sex and age matched hospitalized controls (HC). We evaluated the multihormonal responses to the dopamine agonist apomorphine (APO, 0,75 mg SC) in order to obtain an indirect index of dopaminergic neurotransmission at the post synaptic level. We also examined, in the same subjects, prolactin (PRL) response to 8AM and 11PM protirelin challenges (TRH, 200μg IV) and cortisol response to dexamethasone suppression test (DST, 1 mg orally). No significant difference in cortisol, ACTH and GH values was found between controls, UP and BP patients (i.e. at baseline and in response to apomorphine test). However, BP had lower APO-induced PRL suppression than HC (P =0.0003) and UP (P =0.04). Taken together these results suggest that decreased APO-induced PRL suppression in bipolar depressed patients is not due to deficiency of pituitary lactrophs and/or increased HPA axis activity, but may reflect altered post synaptic receptor sensitivity D2 in the tuberoinfundibular dopamine system.