Temperature-dependent features for in vitro nerve-cord preparations to generate sympathetic nerve discharge (SND). (A) Original traces of the SND envelope. Incubation temperature is indicated at the top of each panel. Upper and lower traces in each panel show envelopes of cervical SND (cSND) and splanchnic SND (sSND), respectively. SNDs were discernible at ≥ 20°C. Adding 24 mM Mg2+ to the bath solution at 25°C reduced SNDs to the level at 10°C. (B) Power spectra of cSND and sSND envelopes at 25°C. Spectra were averaged from 21 experiments. Power spectra of both SNDs were similar, showing a peak at ~1 Hz. Photomicrographs in (C) and (D) show c-Fos protein expression in the dorsal root ganglion and celiac ganglion, respectively. The observation was obtained from a nerve-cord-ganglion preparation that incubated under optimal in vitro conditions for SND genesis (25°C normal aCSF, 3 h). c-Fos-positive cells were absent in the dorsal root ganglion (C), but present in the celiac sympathetic ganglion (D). Scale bars = 30 μm in (C, D).