Effects of hexasulfobutylated C-60 on the thalamic neurons in neonatal ratin vitro

The effects of hexasulfobutylated C-60 (FC4S) on membrane potentials and cu rrents were studied by tight-seal, whole-cell recording in thin slices of t he neonatal rat thalamus. Silent neuron with resting membrane potentials of around -62.4 +/- 0.7 mV was found in whole-cell current clamp recordings. Hexasulfobutylated C-60 depolarized the neuron by a concentration dependent manner. It also (1) prolonged the decay time constant of action potential and (2) decreased the threshold of the directly elicited action potentials of the neuron. Hexasulfobutylated C-60 did not miter the input resistance o f the excitable membrane. In whole-cell voltage clamp studies, depolarizing command pulses from a holding potential of about -70 mV evoked a fast inwa rd current followed by an outward current in the thalamic neurons. Hexasulf obutylated C-60 (30 - 100 mu M) increased the total inward sodium current o f the neuron, while hexasulfobutylated C-60 did not alter the outward potas sium currents in all voltage steps tested. It was concluded that hexasulfob utylated C-60 (1) decreased the threshold of the action potential and (2) p rolonged the decay time constant of the directly elicited action potential of the neonatal rat thalamic neurons. The effect may be closely associated with the Na+ current in thalamic neurons.