Effects of the neuropeptide substance P on sleep, mood, and neuroendocrine measures in healthy young men

Abstract

The neuropeptide substance P (SP) has been supposed to be involved in the etiopathology of affective disorders, mainly because of the finding of increased levels of SP in the cerebrospinal fluid of depressed patients and the preliminary evidence of antidepressant effects of SP-receptor antagonists in depressed patients. We investigated whether SP may induce changes of sleep, mood and neuroendocrine measures that are similar to those in depressed patients. In a double-blind, randomized cross-over design, 12 healthy young men were investigated in two blocks of three consecutive nights, in which SP or NaCl was intravenously infused during the third night. Polysomnographic recordings were obtained during all nights and blood samples were drawn every 30 min during the third night. Infusion of SP caused a significant worsening of the mood of the subjects, led to an increase of REM latency and time awake during the SP-infusion intervals, caused increased stage 1 sleep in the first part of the night, and led to increased cortisol and thyroid stimulating hormone levels and a trend for decreased growth hormone levels. These effects can be interpreted as evidence for a central arousing effect of SP. Further studies should focus on the effects of substance P in patients with depressive or other psychiatric disorders.