Altered dopamine D₂ receptor function in fibromyalgia patients: a neuroendocrine study with buspirone in women with fibromyalgia compared to female population based controls

Abstract 

Background: To what extent fibromyalgia belongs to affective spectrum disorders or anxiety spectrum disorders remains disputed. Buspirone induces a hypothermic response, which most likely is due to 5-HT_1A autoreceptor stimulation, and growth hormone (GH) release, which probably is related to postsynaptic 5-HT_1A receptor stimulation. The prolactin response to buspirone has been suggested to be mediated through dopamine (DA) antagonistic effects. Objectives: Based on the assumption that fibromyalgia is more strongly related to stress and anxiety than affective spectrum disorders, we hypothesized that compared to population controls, fibromyalgia patients should demonstrate an increased prolactin response (DA sensitivity) to buspirone challenge test, but no difference in hypothermic response or GH release (5HT sensitivity). Method: A 60-mg dose of buspirone was given orally to 22 premenopausal women with fibromyalgia and 14 age and sex matched healthy control subjects. Core body temperature, growth hormone and prolactin levels were analyzed at baseline and after 60, 90, and 150 min. Results: Fibromyalgia patients showed an augmented prolactin response to buspirone compared to controls. Temperature and growth hormone responses did not differ from controls. Conclusions: Dopaminergic rather than serotonergic neurotransmission is altered in fibromyalgia, suggesting increased sensitivity or density of dopamine D₂ receptors in fibromyalgia patients. Stress and anxiety is an important modulator of dopaminergic neurotransmission. Our results suggest that fibromyalgia is related to anxiety and associated with disturbance in the stress response systems.

Keywords:  Fibromyalgia, Neuroendocrine challenge, 5-HT1_A-receptors, Dopamine D₂ receptors, Dopamine, Serotonin