Noradrenaline induces rhythmic bursting in sympathetic preganglionic neurons

In the in vitro slice preparation of upper thoracic cord of the cat, noradrenaline, at concentrations of 10-50 microM, induced rhythmic bursting in 30% of sympathetic preganglionic neurons of the intermediolateral nucleus. The bursting frequencies were between 0.2 and 1.0 Hz at membrane potentials between -45 and -65 mV. The bursting rhythm could be reset by short intracellular current pulses. In the presence of tetrodotoxin noradrenaline produced a rhythmic oscillation in membrane potential in the same frequency range as the bursting. The frequency of oscillation was voltage dependent. Neuronal input resistance decreased at the oscillation peak and the oscillation was abolished by cobalt or low calcium.