Adenosine and homeostatic control of sleep. Actions in target structures of the sleep-wake circuits
*Correspondencia: Dra. Isabel de Andrés. Departamento de Anatomía, Histología y Neurociencia. Facultad de Medicina. Universidad Autónoma de Madrid. Arzobispo Morcillo, 4. E-28029 Madrid.
Fax: +34 914 975 338.
E-mail: isabel.deandres@uam.es
Sleep homeostasis occurs during prolonged wakefulness. Drowsiness and sleep pressure are its behavioral manifestations and, when sleep is allowed, there is a sleep rebound of sufficient duration and intensity to compensate for the previous deprivation. Adenosine is one of the molecules involved in sleep homeostasic regulation. Caffeine and theophylline, stimulants widely consumed by the humans, are antagonists. It is an endogenous factor, resulting from ATP metabolism in neurons and glia. Adenosine accumulates in the extracellular space, where it can exert regulatory actions on the sleep-wakefulness cycle circuits. Adenosine acts through the purinergic receptors A1 and A2. This paper reviews: 1) the metabolic pathways of cerebral adenosine, and the mechanisms of its release by neurons and glia to the extracellular space; 2) the actions of adenosine and its antagonists in regions of the central nervous system related to wakefulness, non-REM sleep, and REM sleep, and 3) the synaptic mechanisms involved in these actions.
