Buspirone challenge test

The buspirone challenge test measures how much prolactin is released into the bloodstream when a single dose of the drug buspirone (a 5-HT1A receptor agonist) is orally administered. This test has been shown to distinguish ME/CFS patients from healthy controls, as well as distinguishing ME/CFS patients from patients with depression.

Studies

 * A 1992 study by Bakheit, Behan et al on 15 ME/CFS patients, 13 patients with depression and 13 healthy controls found that buspirone-stimulated prolactin release in patients was significantly higher than in both depressed patients and healthy controls, indicating that the buspirone challenge test can distinguish ME/CFS patients from depressed patients, as well as distinguishing ME/CFS patients from healthy controls. The administration of a single does of buspirone was also found to cause excessive fatigue, lightheadedness and nausea in ME/CFS patients but not in controls. The authors stated that the prolactin release in response to buspirone administration seems to be mediated by 5-hydroxytryptamine (serotonin) receptors since the release can be blocked by specific 5-hydroxytryptamine antagonists such as mnethysergide and metergoline. The authors said their findings are consistent with an increased sensitivity of serotonin receptors in the hypothalamus.
 * In a 1995 study by Dr John Richardson, 25 ME/CFS patients who were positive for enterovirus infection (enteroviral VP1 protein detected in their blood) were administered a buspirone challenge test: the prolactin release in patients was found to be on average 3 times higher than the release in healthy controls, a highly significant difference. Richardson also found that the degree of shift in the sleep/wake cycle that the ME/CFS patients suffered from (which he termed "owl syndrome") correlated with the degree of prolactin release measured in the buspirone challenge.
 * A 1996 study by Sharpe et al found ME/CFS patients had significantly higher plasma prolactin concentrations and experienced more nausea and lightheadedness in response to buspirone than did controls. However, no significant differences in the secretion of growth hormone in response to buspirone were observed between these groups. The authors questioned whether this reflects an increase in hypothalamic serotonin receptor sensitivity because ME/CFS patient growth hormone responses to buspirone were not significantly raised.