Figure 2.

Proposed model for photoperiod-dependent cell rearrangement in the SCN. (a) Schematic of coronal SCN slice showing approximate spatial distributions of AVP, GRP, VIP, and astroglia. GABAergic inputs tend to result in excitatory responses under long photoperiod (left), while responses tend to be inhibitory under short photoperiod (right). (b) Relative mRNA expression levels of Per2, Rev-erbα, AVP, Bmal1, and VIP throughout a circadian cycle under long (left) photoperiod or short (right) photoperiod. Adapted from Ecker et al. [48] and Aton et al. [64]. AVP: arginine vasopressin; Bmal1: brain and muscle ARNT-like protein 1; GABA: gamma-aminobutyric acid; GRP: gastrin-releasing peptide; Per2: period 2; VIP: vasoactive intestinal peptide.