Rhythmic discharge induced by temperature variation and drugs in isolated sympathetic ganglia

Isolated sympathetic ganglia from various mammalian species fire spontaneous, rhythmic discharge when exposed to low temperatures. Extracellular recording from rat, guinea pig, and rabbit superior cervical ganglia as well as dog lumbar ganglion revealed large single potentials or bursts of potentials, occurring at regular intervals, when the bath temperature was kept between 15-30 degrees C. When the temperature was reduced below 15 degrees C or raised above 30 degrees C, the rhythmic discharge decreased in frequency and finally stopped. Rhythmic discharge also appeared when ganglia were treated with emetine or the K(+) channel blockers, cesium and 4-aminopyridine. The frequency and amplitude of potentials and the pattern of rhythm varied from ganglion to ganglion. The single potential or rhythmic burst firing seemed to originate from a single unit or multiple discharging units, as indicated by the amplitude and frequency of the potentials in a burst. The discharge was abolished by ganglionic blocking agents or by the absence of Ca(2+), suggesting a presynaptic origin. The spontaneous rhythmic discharge may be important as a support mechanism for the cardiovascular system in victims of exposure to extreme cold temperature.