Illuminating serotonergic gateways for strong resetting of the mammalian circadian clock

Alcohol usage and abrupt cessation modulate diurnal activity

“…Both in vivo (5,21,45) and in vitro (24,33) experiments have shown that pharmacological intervention with selective ligands for 5-HT receptors produces phase shifts and/or changes in amplitude of the measured rhythm. On the basis of these findings, it is clear that serotonergic innervation of the SCN plays an important part in modulating the activity and output of the circadian oscillator (22,25,35). …”

“…These non-synaptic receptors are more affected because they outnumber synaptic, the synaptic ones and they are more sensitive to fine modulation of ambient in the extracellular space compared with receptors in the synapses (52), the non-synaptic function are thought to be responsible for the modulation, tuning and alteration of many physiological processes such as the level of arousal and may be also circadian activity patterns shown in this study following chronic alcohol consumption. Furthermore, studies have shown (4,25,37,38) that both chronic ethanol intake and ethanol withdrawal may be associated with changes in a fundamental parameter of the circadian pacemaker (3,31). The results of this study further supports the evidence that ethanol alters the circadian rhythm.…”

Serotonin Increases the Phase Shift of the Circadian Locomotor Activity Rhythm in Mice after Dark Pulses in Constant Light Conditions

“…In another experiment, exposure of hamsters to two days of LL significantly increased the magnitude of circadian phase shifts induced by nonphotic stimuli, such as the 8-OH-DPAT administered during the day at ZT0, ZT3 and ZT6 (Zeitgeber Zeit 0 was defined arbitrarily as the onset of light phase), and then after injection, the animals were immediately transferred to constant darkness (KNOCH et al 2004;DUNCAN et al 2005). The brief constant light treatment markedly enhanced both the amplitude of 8-OH-DPAT induced phase advance and the sensitivity of the animals to the drug, and appears to open the 5-HT 1A window to clock (SCN) resetting that is not readily accessible under normal light conditions or in constant darkness (KNOCH et al 2006;MISTLBERGER 2006).…”