The neuroendocrinological profile of roxindole, a dopamine autoreceptor agonist, in schizophrenic patients

Roxindole is a potent autoreceptor-selective dopamine agonist with additional properties as a serotonin reuptake inhibitor and 5-HT1A agonist. In order to get more insight into its mode of action in various psychiatric populations, we evaluated the effects of subchronic roxindole treatment on pituitary and adrenal hormone secretion, i.e. release of prolactin, thyroid stimulating hormone (TSH), growth hormone (GH), luteinizing hormone (LH), and cortisol. Fifteen schizophrenic patients with positive and negative symptomatology, respectively, were treated with roxindole for 28 days. Both basal and thyrotropin releasing hormone (TRH) -induced prolactin secretion diminished significantly to 26.4% and 22.8% of baseline levels, respectively, under roxindole. Basal GH secretion was insignificantly elevated by 89%, whereas GH levels increased nearly 3-fold after stimulation by TRH. TSH levels decreased insignificantly to 57.5% of baseline levels, while TRH-induced TSH release was not affected by subchronic roxindole. Roxindole treatment influenced neither LH secretion nor cortisol release. Our results indicate that roxindole's dopaminergic actions might prevail over its serotonergic effects, at least as far as the regulation of anterior pituitary hormone secretion is concerned.