Peripheral Serotonin in Alzheimer’s Disease

Abstract

The platelet has been suggested to be a peripheral model of the central seroton-ergic neuron. This investigation was carried out in order to test the hypothesis that levels of serotonin (5-HT) in the platelet will be decreased in Alzheimer’s disease (AD) since neurochemical studies suggest that levels of 5-HT are decreased in the brain of AD patients. We investigated platelet and plasma 5-HT in a group of AD patients (n = 22) as well as in age-matched normal control subjects (n = 20). The results show that the platelet level of 5-HT was significantly reduced in AD (65.7 ± 28.41 ng/10⁸ platelets in AD vs. 112.9 ± 35.11 ng/10⁸ platelets in controls; p = 0.0001). There was no effect on the levels of its metabolite 5-hydroxyindoleacetic acid. These findings suggest that the peripheral serotonergic system in AD is adversely affected.

Platelet serotonin concentration and monoamine oxidase type B activity in female patients in early, middle and late phase of Alzheimer's disease

“…This finding is in agreement with alike platelet 5-HT concentrations in patients with early or late onset AD (Mimica et al 2005), but in contrast with decreased platelet 5-HT concentration in patients with AD (Kumar et al 1995), and increased platelet 5-HT concentrations in demented patients with delusions (Meszaros et al 1998) compared to 5-HT values in healthy controls. The explanation for the discrepancies between studies should be sought in different diagnoses (AD vs. dementia) and presence of delusions ( (Meszaros et al 1998), which were reported to increase platelet 5-HT concentration (Pivac et al 2006b).…”

“…The explanation for the discrepancies between studies should be sought in different diagnoses (AD vs. dementia) and presence of delusions ( (Meszaros et al 1998), which were reported to increase platelet 5-HT concentration (Pivac et al 2006b). In addition, previous studies (Kumar et al 1995;Meszaros et al 1998) included smaller number of patients and control subjects, the severity of AD was not specified, and different methods i.e. fluorimetric (Mimica et al 2005) or HPLC (Kumar et al 1995;Meszaros et al 1998) were used for the determination of platelet 5-HT concentrations.…”

“…In addition, previous studies (Kumar et al 1995;Meszaros et al 1998) included smaller number of patients and control subjects, the severity of AD was not specified, and different methods i.e. fluorimetric (Mimica et al 2005) or HPLC (Kumar et al 1995;Meszaros et al 1998) were used for the determination of platelet 5-HT concentrations.…”

“…The studies on platelet 5-HT concentration and platelet MAO-B activity in AD yielded inconsistent results. The increased (Meszaros et al 1998), decreased Kumar et al 1995) or unaltered (Mimica et al 2005) platelet 5-HT concentrations, as well as increased (Adolfsson et al 1980) or unaltered (Ahlskog et al 1996) platelet MAO-B activity were observed in AD. Our recent studies showed that platelet MAO-B activity might be used as a biomarker for the presence of psychotic features in AD (Mimica et al 2008), and for the early or late onset AD (Mimica et al 2005).…”

Serum level of serotonin during rest and during exercise in paraplegic patients

“…10 ± 14 Several chronic neurological conditions such as multiple sclerosis, Alzheimer's disease and trigeminal neuralgia are associated with changes in platelet-and serum serotonin. 12,15 No di erences were found between the active and inactive groups, while Soares et al 16 reported higher serum 5-HT levels during rest in trained than in untrained ablebodied individuals. Di erences in training status of the subjects between the studies might have accounted for the discrepant results, since the active group of their study was constituted of national and international track and ®eld able-bodied athletes, while in the current study recreational athletes were included.…”