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Sleep deprivation (SD) is a technique of sleep-wake manipulation which has been used to treat depression. Changes in neurotransmitter systems, that are also involved in the effects of the antidepressant drugs, have been suggested as the possible mechanisms of action of SD. However, the therapeutic effect of SD is acute and transient, while antidepressant effects of drug treatments are gradual and stable. SD might work throughout mechanisms that are different from those mediating drug's effects. In the present study we analyzed the role of dopamine activity in SD. Spontaneous eye blink rate provides a non invasive measure of central dopamine activity. We assessed eye blink rate across prolonged wakefulness (from 10:00 a.m. to 07:00 a.m.) in 25 young normal subjects. Eye blink rate increased at the end of the wakefulness period. Blink rates and sleepiness as assessed by Karolinska Sleepiness Scale correlated positively with time spent awake. We propose that increased blink rate might reflect a dopamine activation that counteracts sleep drive. Antidepressant effects of sleep deprivation might be related to activation of the physiological mechanisms which regulate wake maintenance.

Objective: To examine the effects of vibroacoustic stimulation (VAS) on fetal heart rate (FHR) in term human fetuses by computerized carditocography system., Methods: FHR was analyzed 20 min before and 30 min after vibroacoustic stimulation using the Oxford Sonicaid System 8002 for computerized FHR measurement. Recordings were made in 31 uncomplicated pregnancies at 36-42 weeks' gestation., Results: Vibroacustic stimulation of the fetus evoked a significant increase in all the parameters evaluated (number of fetal movements, of accelerations above 10 and 15 bpm, in high- and low-variability episodes, and in short-term variations). Concerning the effect of behavioural states on the response to VAS, some changes (FHR, high-variability episodes) occurred independently of behavioural states, while other parameters (accelerations >10 and 15 bpm: short-term variation) underwent statistically significant changes only for behavioural states 1F and 2F., Conclusions: Our study supports the hypothesis of a significant fetal response in normal term pregnancy, as clearly shown by computerized cardiotocography. The immediate response occurred independently of behavioural states, although some differences were present (mainly for F1 and F2 states) if the evaluation was extended in time.