Increased imidazoline and α₂ adrenergic binding in platelets of women with dysphoric premenstrual syndromes

An association between dysphoric premenstrual syndromes (PMS) and a lifetime history of major depressive disorders has previously been documented. Other studies have demonstrated an increase in the binding of radiolabeled imidazoline compounds to platelets of depressed patients. Clonidine and related imidazoline compounds interact with α₂ adrenoceptors to inhibit neuronal noradrenergic activity and in higher concentrations, they stimulate noradrenergic activity through their interaction with imidazoline receptors. Here we report increased ³H para-aminoclonidine binding to high affinity α₂ adrenoceptor sites as well as to noradrenergic imidazoline binding sites in platelets of women with dysphoric PMS. This higher binding was most pronounced during the late-luteal-symptomatic phase of the menstrual cycle and, to a lesser degree, during the non-symptomatic mid-follicular phase. Binding to the imidazoline site distinguished women with dysphoric PMS from women with no such symptoms, was highly positively correlated with the severity of symptoms, and was negatively correlated with plasma levels of progesterone. These findings suggest that platelet imidazoline binding sites might be a biological marker for dysphoric states in PMS or for the vulnerability to develop them. These findings also point to a possible biological link between dysphoric PMS and major depressive disorders.