Fig. 1.

Enhanced activity is a characteristic of midline anterior thalamic paraventricular nucleus (aPVT) neurons from the night period. In this and subsequent figures, red symbols, traces, and histograms pertain to data on aPVT neurons in slices prepared during the subjective day period [zeitgeber time (ZT) 2–6], and black symbols, traces, and histograms pertain to data on neurons in slices prepared during the night period (ZT 14–18). A: representative whole cell current-clamp traces from 3 different aPVT neurons illustrate the different spontaneous patterns (silent, bursting, and tonic) observed during the initial 5 min of recordings, with corresponding ratemeter records below. Corresponding resting membrane potentials were −65 mV (silent cell; day period), −63 mV (burst firing; night period), and −50 mV (tonic firing cell; night period). Inset depicts higher temporal resolution (500 ms) of a typical low-threshold spike (LTS) crowned with sodium spikes. B: horizontal bars along the ZT axis (bottom) correspond to times for brain slice preparation (ZT 2–6, day or ZT 14–18, night). Dots in the modes of activity graph (top) represent the actual ZT times for whole cell recordings for all aPVT neurons. C: histograms illustrate the percentile distribution of silent and active neurons from both ZT periods, with numbers of cells indicated within the bars. Statistical comparisons were performed using the χ² test.