Abstract

Since the early observations made by Santiago Ramon y Cajal more than a century ago till now, astrocytes have gradually gained protagonism as essential partners of neurons in building brain circuits that regulate complex behavior. In mammals, processes such as sleep–wake cycle, locomotor activity, cognition and memory consolidation, homeostatic and hedonic appetite and stress response (among others), are synchronized in 24‐h rhythms by the circadian system. In such a way, physiology efficiently anticipates and adapts to daily recurring changes in the environment. The hypothalamic suprachiasmatic nucleus (SCN) is considered the central pacemaker, it has been traditionally described as a nucleus of around 10,000 neurons nearly all GABAergic able to be entrained by light and to convey time information through multiple neuronal and hormonal pathways. Only recently, this neuro‐centered view was challenged by breakthrough discoveries implicating astrocytes as essential time‐keepers. In the present review, we will describe the current view on the SCN circuit and discuss whether astrocytic functions described in other brain regions and state‐of‐the‐art experimental approaches, could help explaining better those well‐ and not so well‐known features of the central pacemaker.