Circadian modulation of membrane properties in slices of rat suprachiasmatic nucleus

PERFORATED patch clamp recordings of neurons in slices of the suprachiasmat ic nucleus (SCN) were made in their subjective day and night phases. The sp ontaneous firing rate and input resistance were significantly higher during the subjective day as compared to the subjective night. Ln parallel, the m embrane potential of neurons recorded at daytime was significantly more dep olarized than at nighttime. The day-night differences in membrane potential and input resistance were maintained when spikes and GABAA receptor-mediat ed transmission were blocked by tetrodotoxin and bicuculline, suggesting a cell-autonomous regulation of the circadian modulation of membrane properti es. In conclusion, these findings suggest that at least one hyperpolarizing ionic conductance would be open at night and closed during mid-day, when s pontaneous firing reaches peak levels in the SCN. NeuroReport 9: 3725-3729 (C) 1998 Lippincott Williams & Wilkins.