Likewise, plasticity in the temporal organization of neural

circuits is proposed to be critical for the context-specific regulation of behavior and physiology (Buzsáki, 2006). Further, dysfunction in the process of neuronal synchronization is implicated in epilepsy and cognitive impairment (Schnitzler and Gross, 2005). Since the principles of neural synchronization apply to systems operating on a range of timescales (Buzsáki and Draguhn, 2004 and Hansel et al., 1995), our study highlights organizational principles that may be relevant for other oscillatory networks (Buzsáki, 2006). All procedures were approved by CP-690550 molecular weight the Institutional Animal Care and Use Committee of the trans-isomer clinical trial Morehouse School of Medicine in accordance with the guidelines of the U.S. National Institutes of Health. Homozygous PERIOD2::luciferase (PER2::LUC) knockin mice (Yoo et al., 2004), backcrossed to a C57Bl/6J background, were

bred and raised under a 24 hr light:dark cycle with 12 hr light and 12 hr darkness (LD12:12, lights on: 0600 EST). Ambient room temperature was maintained at 22°C ± 2°C, and the animals had ab libitum access to water and food (Purina Rodent Chow #5001). For all experiments, adult male PER2::LUC mice (7–9 weeks of age) were transferred to individual wheel-running cages contained within light-tight secondary enclosures. Long-day photoperiods were achieved by an abrupt and symmetrical reduction of the scotophase. Mice were entrained to LD12:12, LD16:8, LD18:6, LD20:4, or LD22:2 for 12 weeks.

LD20:4 entrainment for less than 12 weeks produced SCN reorganization, but with individual differences in whether the pattern was evident Liothyronine Sodium (data not shown). Wheel-running rhythms were monitored and analyzed with the Clocklab data collection and analysis system (Actimetrics). Coronal SCN slices (150 μm) were collected and imaged as described previously (Evans et al., 2011). Unless otherwise stated, mice were sacrificed 2–4 hr before lights-off, since dissections during late subjective day do not reset the phase of the SCN (Davidson et al., 2009). Each SCN slice was cultured on a membrane (Millicell-CM; Millipore) with 1.2 ml of air-buffered medium containing 0.1 mM beetle luciferin (Gold Biotechnologies) and imaged for 5–7 days using a Stanford Photonics XR Mega 10Z cooled intensified charge-coupled device camera. For drug treatments, TTX (2.5 μM, catalog No. 1069; Tocris), the VIP receptor antagonist [4Cl-D-Phe6, Leu17] VIP (20 μM, catalog No. 3054; Tocris), or BIC (200 μM, catalog No. B7686; Sigma) was added to the culture medium and remained for the duration of the recording. For each pharmacological agent, drug dose was selected from published literature (Atkins et al., 2010, Aton et al., 2006 and Yamaguchi et al., 2003), and we independently validated dose efficacy in our preparation (Figures S6A–S6C).