Ultradian variation of nerve growth factor plasma levels in healthy and schizophrenic subjects.

Some studies in animal models showed that several neurotrophins may be implicated in the regulation
of light-dependent suprachiasmatic pacemaker and in other functions implicated in long-term memory
acquisition during sleep. However, no data are known about the role played by NGF in ultradian regulation
in humans. The aim of this study was to investigate whether or not there is a natural diurnal fluctuation
during daytime in healthy and schizophrenic subjects with a normal light/dark cycle. In a sample of 33
subjects (10 male schizophrenics and 23 healthy subjects) an ELISA assay was used to study the ultradian
NGF cycle in blood samples at 9.00, 13.00 and 20.00 hours. The study showed an ultradian rhythm of NGF
in healthy subjects with a “V” trend: higher at 9:00 and 20:00 and lower at 13:00. We also show significant
differences between male and female controls. No NGF ultradian rhythm among schizophrenic patients
compared to healthy subjects was found. The results of this study lead to a rhythmic NGF regulation that
appears altered in schizophrenics, where higher levels in the morning and lower levels in the evening were
observed, compared to the controls, and support the hypothesis of a role played by NGF in schizophrenia.